In a trial at a district hospital, 50 children with acute diarrhoea receive ORS with zinc and 50 receive ORS alone. Diarrhoea lasts more than 5 days in 10 children given zinc and in 30 given ORS alone. What is the chi-square value, and what is the conclusion at the 5% level (table value 3.84)?

16.7; the difference is significant

16.7; the difference is not significant

3.84; the difference is borderline

8.3; the difference is significant

Biostatistics: data, sampling and tests of significance

30 NEET-PG practice questions on Biostatistics: data, sampling and tests of significance, part of Community Medicine. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Medium
In a school survey under Anaemia Mukt Bharat, the haemoglobin of 400 adolescent girls follows a normal distribution with a mean of 11.0 g/dL and a standard deviation of 1.0 g/dL. About how many girls have haemoglobin between 9.0 and 13.0 g/dL?
1. AAbout 380
2. BAbout 272
3. CAbout 200
4. DAbout 399
Show answerHide answer
Answer: A · About 380
In a normal distribution, about 68% of values lie within 1 SD of the mean, about 95% within 2 SD and about 99.7% within 3 SD. The range 9.0-13.0 g/dL is the mean plus or minus 2 SD, so about 95% of 400, that is 380 girls, fall within it. The remaining 5% are split equally between the tails, so about 10 girls have haemoglobin below 9.0 g/dL. The mean, median and mode coincide in a normal curve.
- B: 272 is 68% of 400, the share within 1 SD.
- C: 200 is half the girls, those above or below the mean.
- D: 399 is 99.7% of 400, the share within 3 SD.
Question 2 · Hard
In a trial at a district hospital, 50 children with acute diarrhoea receive ORS with zinc and 50 receive ORS alone. Diarrhoea lasts more than 5 days in 10 children given zinc and in 30 given ORS alone. What is the chi-square value, and what is the conclusion at the 5% level (table value 3.84)?
1. A16.7; the difference is not significant
2. B3.84; the difference is borderline
3. C16.7; the difference is significant
4. D8.3; the difference is significant
Show answerHide answer
Answer: C · 16.7; the difference is significant
Row totals are 50 and 50, and column totals are 40 (prolonged) and 60 (not prolonged), out of 100. Expected values are 20 and 30 in each row, so chi-square = (10 - 20)squared/20 + (40 - 30)squared/30 + (30 - 20)squared/20 + (20 - 30)squared/30 = 5 + 3.33 + 5 + 3.33 = 16.7. With 1 degree of freedom this is far above 3.84, so p is below 0.05 and the difference is significant. Zinc shortens the duration of diarrhoea, which is why it is given with ORS.
- A: A value above 3.84 is significant at the 5% level.
- B: 3.84 is the table value, not the calculated chi-square.
- D: 8.3 adds only two of the four cells.
Question 3 · Medium
A statistics teacher asks postgraduates to match parametric tests with their non-parametric counterparts: 1. Paired t-test with the Wilcoxon signed-rank test. 2. Unpaired t-test with the Mann-Whitney U test. 3. One-way ANOVA with the Kruskal-Wallis test. 4. Pearson correlation with Spearman rank correlation. Which pairs are correctly matched?
1. A1, 2 and 4 only
2. B1, 2, 3 and 4
3. C2 and 4 only
4. D1 and 3 only
Show answerHide answer
Answer: B · 1, 2, 3 and 4
All four pairs are correct. Non-parametric tests use ranks rather than raw values, so they do not assume a normal distribution and suit ordinal or skewed data. The Wilcoxon signed-rank test replaces the paired t-test, the Mann-Whitney U test the unpaired t-test, the Kruskal-Wallis test one-way ANOVA, and Spearman's rank correlation Pearson's correlation. They are slightly less powerful than parametric tests when the data really are normal.
- A: Pair 3, ANOVA with Kruskal-Wallis, is also correct.
- C: Pairs 1 and 3 are also correct.
- D: Pairs 2 and 4 are also correct.
Question 4 · Medium
In a district hospital, the length of stay of 1,000 admitted patients is recorded: most stay 2-4 days, but a few stay for several weeks. How will the mean, median and mode relate to each other?
1. AMode < median < mean
2. BMean < median < mode
3. CMean = median = mode
4. DMean < mode < median
Show answerHide answer
Answer: A · Mode < median < mean
A few very long stays create a long tail to the right, a positively skewed distribution. The mean is pulled towards the tail, so it is the largest; the mode sits at the peak, and the median lies between them. In a negatively skewed distribution the order is reversed, and in a normal distribution all three are equal. For such data the median and interquartile range describe the centre and spread better.
- B: This order fits a negatively (left) skewed distribution.
- C: All three are equal only in a symmetrical distribution.
- D: The median always lies between the mean and the mode in a skewed distribution.
Question 5 · Easy
A survey finds anaemia in 120 of 300 adolescent girls in one block and in 90 of 300 in another. Which test of significance is most appropriate to compare the two proportions?
1. AChi-square test
2. BUnpaired t-test
3. CPearson correlation
4. DPaired t-test
Show answerHide answer
Answer: A · Chi-square test
The outcome, anaemic or not, is a qualitative (categorical) variable, and the two groups are independent, so the proportions are compared with the chi-square test (or a z-test for two proportions). t-tests compare means of quantitative data. Correlation measures the association between two quantitative variables. For a 2x2 table with small expected numbers, Fisher's exact test is used instead.
- B: The unpaired t-test compares means, not proportions.
- C: Correlation relates two quantitative variables.
- D: The paired t-test compares means in matched or before-after data.
Question 6 · Medium
In a school health survey, haemoglobin has a mean of 12 g/dL with an SD of 1.2 g/dL, and height has a mean of 150 cm with an SD of 6 cm. The medical officer wants to know which variable is relatively more variable. What should he conclude?
1. AHeight, because its SD is larger
2. BHeight, with a coefficient of variation of 10%
3. CHaemoglobin, with a coefficient of variation of 10%
4. DBoth, as they cannot be compared
Answer and explanation in LearnFree account
Question 7 · Medium
A district team plans a survey to estimate the prevalence of hypertension in adults, expected to be about 20%, with an allowable absolute error of 4 percentage points at 95% confidence (z taken as 2). What sample size is needed?
1. A100
2. B6,400
3. C400
4. D1,600
Answer and explanation in LearnFree account
Question 8 · Easy
For a household survey, a medical officer must select 60 of the 1,200 households in a village using systematic random sampling. What is the sampling interval?
1. A60
2. B20
3. C12
4. D120
Answer and explanation in LearnFree account
Question 9 · Medium
A trial at a medical college reports that a new antiemetic reduced vomiting compared with ondansetron, p = 0.03. A postgraduate lists four interpretations: 1. If there were truly no difference, results this extreme or more would occur about 3% of the time. 2. The new drug is proven to be better. 3. The p value does not show how large the effect is. 4. There is a 97% probability that the new drug works. Which interpretations are correct?
1. A1, 2 and 4 only
2. B1 and 3 only
3. C2 and 3 only
4. D1 and 4 only
Answer and explanation in LearnFree account
Question 10 · Easy
In a survey of anaemia in pregnant women at a CHC, each woman is classed as having no, mild, moderate or severe anaemia. On which scale of measurement are these data?
1. AInterval
2. BRatio
3. COrdinal
4. DNominal
Answer and explanation in LearnFree account
Question 11 · Easy
A district hospital records the birth weights of 500 consecutive newborns and wants to show how often each range of weight occurs. Which diagram is most appropriate?
1. AHistogram
2. BPie chart
3. CBar chart
4. DScatter diagram
Answer and explanation in LearnFree account
Question 12 · Medium
A nutrition study compares the mean weight gain of children on three different supplementary diets at Anganwadi centres. A student lists four points: 1. One-way ANOVA is a suitable test. 2. Doing repeated t-tests between pairs raises the overall chance of a type I error. 3. A significant ANOVA result shows which pair of diets differs. 4. ANOVA assumes roughly normal data with similar variances. Which points are correct?
1. A1, 2 and 4 only
2. B1 and 3 only
3. C2, 3 and 4 only
4. D3 and 4 only
Answer and explanation in LearnFree account
Question 13 · Medium
A pilot study at a tertiary hospital compares a rare adverse reaction between two drugs in 24 patients; in the 2x2 table, two cells have expected frequencies below 5. Which test is most appropriate?
1. AMcNemar's test
2. BUnpaired t-test
3. CChi-square without correction
4. DFisher's exact test
Answer and explanation in LearnFree account
Question 14 · Medium
At an urban PHC, 30 hypertensive adults have their systolic blood pressure measured before and after 12 weeks of a yoga programme, and the differences are approximately normally distributed. Which test should be used to see whether blood pressure has fallen?
1. ATwo-sample (unpaired) t-test
2. BChi-square test of association
3. CMann-Whitney U test
4. DPaired t-test
Answer and explanation in LearnFree account
Question 15 · Hard
In a district, birth weights of 2,000 term babies are normally distributed with a mean of 2.9 kg and an SD of 0.4 kg. About how many of these babies weigh less than 2.1 kg?
1. AAbout 320
2. BAbout 100
3. CAbout 50
4. DAbout 5
Answer and explanation in LearnFree account
Question 16 · Medium
In a trial at a medical college, pain after surgery is scored by patients on a 0-10 scale; the scores are strongly skewed. The scores of two independent groups, one given drug A and one given drug B, are to be compared. Which test is most appropriate?
1. AMann-Whitney U test
2. BUnpaired t-test
3. CKruskal-Wallis test
4. DWilcoxon signed-rank test
Answer and explanation in LearnFree account
Question 17 · Medium
A study at a district hospital compares the mean birth weight of 80 babies born to anaemic mothers with that of 80 babies born to non-anaemic mothers; birth weights are normally distributed. Which test is appropriate?
1. AChi-square test
2. BSpearman rank correlation
3. CUnpaired (independent) t-test
4. DPaired t-test
Answer and explanation in LearnFree account
Question 18 · Medium
A small trial of 30 patients at a district hospital finds that a new drug lowers HbA1c by 0.3% more than the standard drug, but the result is not statistically significant (p = 0.20). A larger trial later confirms a real benefit. What was the most likely problem with the small trial?
1. ALow power leading to a type II error
2. BA type I error from a low alpha
3. CSelection bias from randomisation
4. DConfounding by indication
Answer and explanation in LearnFree account
Question 19 · Medium
In a village, 200 adults are asked whether they use iodised salt before and after a health education campaign, and each person's answers before and after are compared. Which test is appropriate to judge the change in the proportion using iodised salt?
1. APaired t-test
2. BFisher's exact test
3. CMcNemar's test
4. DChi-square test for independence
Answer and explanation in LearnFree account
Question 20 · Hard
A study plans to estimate the mean systolic blood pressure of adolescents in a district. A pilot study gives an SD of 12 mm Hg, and the mean is to be estimated within plus or minus 2 mm Hg with 95% confidence (z taken as 2). What sample size is needed?
1. A144
2. B36
3. C576
4. D288
Answer and explanation in LearnFree account
Question 21 · Medium
To evaluate immunisation coverage in a district, 30 villages are chosen with probability proportional to population size, and 7 children aged 12-23 months are surveyed in each. What sampling method is this?
1. ASystematic random sampling
2. BCluster sampling
3. CStratified random sampling
4. DSimple random sampling
Answer and explanation in LearnFree account
Question 22 · Medium
A sample of 100 adult men in a town has a mean systolic blood pressure of 120 mm Hg with a standard deviation of 10 mm Hg. Within which range does the population mean lie with about 95% confidence?
1. A119 to 121 mm Hg
2. B100 to 140 mm Hg
3. C118 to 122 mm Hg
4. D110 to 130 mm Hg
Answer and explanation in LearnFree account
Question 23 · Hard
A randomised trial of a salt-substitute programme in a block finds that systolic blood pressure fell by a mean of 4 mm Hg more in the intervention group than in the control group, with a 95% confidence interval of -1 to 9 mm Hg. What is the correct interpretation?
1. ASignificant at 5%, as the mean fall is 4 mm Hg
2. BNot significant at 5%, as the interval includes zero (no effect)
3. CNot significant at 5%, as the interval excludes 4
4. DSignificant at 5%, as most of the interval is positive
Answer and explanation in LearnFree account
Question 24 · Hard
A researcher compares the length of stay after caesarean section in three district hospitals. Most women stay 3-5 days, but a few with complications stay over 3 weeks, so the data are strongly skewed. Which test should be used to compare the three hospitals?
1. AKruskal-Wallis test
2. BOne-way ANOVA
3. CMann-Whitney U test
4. DChi-square test
Answer and explanation in LearnFree account
Question 25 · Medium
A survey classifies 600 adults by tobacco use (smoked, smokeless, both, none) and by oral health status (normal, leukoplakia, other lesion), and applies a chi-square test. How many degrees of freedom does the test have?
1. A6
2. B8
3. C11
4. D12
Answer and explanation in LearnFree account

5 more Biostatistics: data, sampling and tests of significance questions

Answer them one by one, keep your score and see your weak topics in Learn. Signed-out visitors try 25 per exam; sign in with Google to see them all.

Study Community Medicine

Biostatistics: data, sampling and tests of significance

In a school survey under Anaemia Mukt Bharat, the haemoglobin of 400 adolescent girls follows a normal distribution with a mean of 11.0 g/dL and a standard deviation of 1.0 g/dL. About how many girls have haemoglobin between 9.0 and 13.0 g/dL?

In a trial at a district hospital, 50 children with acute diarrhoea receive ORS with zinc and 50 receive ORS alone. Diarrhoea lasts more than 5 days in 10 children given zinc and in 30 given ORS alone. What is the chi-square value, and what is the conclusion at the 5% level (table value 3.84)?

In a district hospital, the length of stay of 1,000 admitted patients is recorded: most stay 2-4 days, but a few stay for several weeks. How will the mean, median and mode relate to each other?

A survey finds anaemia in 120 of 300 adolescent girls in one block and in 90 of 300 in another. Which test of significance is most appropriate to compare the two proportions?

In a school health survey, haemoglobin has a mean of 12 g/dL with an SD of 1.2 g/dL, and height has a mean of 150 cm with an SD of 6 cm. The medical officer wants to know which variable is relatively more variable. What should he conclude?

A district team plans a survey to estimate the prevalence of hypertension in adults, expected to be about 20%, with an allowable absolute error of 4 percentage points at 95% confidence (z taken as 2). What sample size is needed?

For a household survey, a medical officer must select 60 of the 1,200 households in a village using systematic random sampling. What is the sampling interval?

In a survey of anaemia in pregnant women at a CHC, each woman is classed as having no, mild, moderate or severe anaemia. On which scale of measurement are these data?

A district hospital records the birth weights of 500 consecutive newborns and wants to show how often each range of weight occurs. Which diagram is most appropriate?

A pilot study at a tertiary hospital compares a rare adverse reaction between two drugs in 24 patients; in the 2x2 table, two cells have expected frequencies below 5. Which test is most appropriate?

At an urban PHC, 30 hypertensive adults have their systolic blood pressure measured before and after 12 weeks of a yoga programme, and the differences are approximately normally distributed. Which test should be used to see whether blood pressure has fallen?

In a district, birth weights of 2,000 term babies are normally distributed with a mean of 2.9 kg and an SD of 0.4 kg. About how many of these babies weigh less than 2.1 kg?

In a trial at a medical college, pain after surgery is scored by patients on a 0-10 scale; the scores are strongly skewed. The scores of two independent groups, one given drug A and one given drug B, are to be compared. Which test is most appropriate?

A study at a district hospital compares the mean birth weight of 80 babies born to anaemic mothers with that of 80 babies born to non-anaemic mothers; birth weights are normally distributed. Which test is appropriate?

A small trial of 30 patients at a district hospital finds that a new drug lowers HbA1c by 0.3% more than the standard drug, but the result is not statistically significant (p = 0.20). A larger trial later confirms a real benefit. What was the most likely problem with the small trial?

In a village, 200 adults are asked whether they use iodised salt before and after a health education campaign, and each person's answers before and after are compared. Which test is appropriate to judge the change in the proportion using iodised salt?

A study plans to estimate the mean systolic blood pressure of adolescents in a district. A pilot study gives an SD of 12 mm Hg, and the mean is to be estimated within plus or minus 2 mm Hg with 95% confidence (z taken as 2). What sample size is needed?

To evaluate immunisation coverage in a district, 30 villages are chosen with probability proportional to population size, and 7 children aged 12-23 months are surveyed in each. What sampling method is this?

A sample of 100 adult men in a town has a mean systolic blood pressure of 120 mm Hg with a standard deviation of 10 mm Hg. Within which range does the population mean lie with about 95% confidence?

A randomised trial of a salt-substitute programme in a block finds that systolic blood pressure fell by a mean of 4 mm Hg more in the intervention group than in the control group, with a 95% confidence interval of -1 to 9 mm Hg. What is the correct interpretation?

A researcher compares the length of stay after caesarean section in three district hospitals. Most women stay 3-5 days, but a few with complications stay over 3 weeks, so the data are strongly skewed. Which test should be used to compare the three hospitals?

A survey classifies 600 adults by tobacco use (smoked, smokeless, both, none) and by oral health status (normal, leukoplakia, other lesion), and applies a chi-square test. How many degrees of freedom does the test have?