Question

Chose the corectt answer(s) questions (1-3)

Question 1

Which of the following statements is true? (Select all correct answers)

		If the mean of two groups remains the same, the P value will not change even if the sample size (n) of those two groups changes.
		The P value is the probability that the alternative hypothesis is true.
		In a study of comparing the amount of alcohol consumed by men and women the null hypothesis would be defined as: “There is no difference in drinking rates of men and women”.
		“Statistically significant” is a term that describes a rejection of the null hypothesis based on a P value of less than 0.05.
		A P-value must have a value of 0.95 or greater to be considered “Statistically significant.”
		In a study of comparing the heights of men and women the alternative hypothesis would be defined as: “The height of men is greater than women”.

Question 2

In a study of workplace bullying in a community NHS trust, staff were asked about whether workplace bullying had affected their working environment (Quine L, BMJ 1999; 318: 228-229). Staff who had been bullied had lower levels of job satisfaction (mean 10.5 [SD 2.7] vs 12.2 [2.3], P<0.001) and higher levels of job-induced stress (mean 22.5 [SD 6.1] v 16.9 [5.8], P<0.001) than those who had not been bullied. Select all of the following statements which you believe to be true.

		P < 0.001 means that there is a less than 1 in 1000 chance that we would have obtained these results, or more extreme results, if the alternative hypothesis was true
		A suitable null hypothesis for this would be that staff in the population who have been bullied at work have similar levels of job satisfaction to staff in the population who have not been bullied at work.
		We can conclude that work place bullying causes lower levels of job satisfaction and higher levels of job-induced stress.
		There is a significant difference in the levels of job satisfaction between those who had and those who had not been bullied
		We cannot reject the null hypothesis at the 5% level of significance.

Question 3

Which of the following will tend to decrease the P-value when two groups are being compared? (Select all correct answers)

		A smaller variance in the samples of both groups
		An increase in the n of each group.
		An increase in the n of one group.
		A larger mean difference between groups

Answer 1

question 1

1) false

if sample sizes change, value of test statistic changes, resulting in change of p value

2) false

p value is the probabiity of observing that sample value given null hypothesis is true

3) true

null hypothesis is the hypothesis of no difference

4)true

if p value less than 0.05 , we reject the null hypothesis

5)false

p value less than 0.05 is considered significant

6)true

question 2

1) false

p value is the probability of observing these results if null hypothesis was true

2) true

3) true

as p vlue is less than 0.001( significant)

4)true

5) false

P value < 0.001 means it is much less than 0.05 , so we reject null hypothesis