Clinical Trials

7. Statistics

Exercise 8

The statements below are about P-values or confidence intervals. Indicate whether each statement is True or False.

The statements are:

• When the P value is less than the threshold level it implies one treatment is statistically significantly different to another:
• A narrow confidence interval implies a small sample size:
• 95% confidence interval for a difference between two population means that includes 0, implies that the p-value from a statistical test of a difference will be less than 0.05:
• 95% confidence intervals are about two standard errors either side of the study mean:
• P being less than 5% indicates a clinical significance:
• A confidence interval containing 0 suggests no statistical significant difference:
• The null hypothesis should be rejected when the P-value is below the significance level:
• 95% confidence interval will include 95% of the observations in the sample:
• A P-value can give insights into whether the trial was adequately powered to answer the original question:
• A P-value can say how effective or different a new treatment is compared with the standard treatment:

Answers:

• When the P value is less than the threshold level it implies one treatment is statistically significantly different to another:
  [True]
• A narrow confidence interval implies a small sample size:
  [False: a narrow confidence interval implies a large sample size.]
• 95% confidence interval for a difference between two population means that includes 0, implies that the p-value from a statistical test of a difference will be less than 0.05:
  [False: A confidence interval for a difference between two population means that includes 0, implies that the P-value from a statistical test of difference will be greater that 0.05.]
• 95% confidence intervals are about two standard errors either side of the study mean:
  [True]
• P being less than 5% indicates a clinical significance:
  [False: If P is less than 5% it indicates a statistical significance.]
• A confidence interval containing 0 suggests no statistical significant difference:
  [True]
• The null hypothesis should be rejected when the P-value is below the significance level:
  [True]
• 95% confidence interval will include 95% of the observations in the sample:
  [False: A 95% confidence interval indicates that there is 95% chance that the population parameter will fall within this interval.]
• A P-value can give insights into whether the trial was adequately powered to answer the original question:
  [It is the probability of the observed result, one or more extreme, when the null hypothesis is true]
• A P-value can say how effective or different a new treatment is compared with the standard treatment:
  [It is the probability of the observed result, or one more extreme, when the null hypothesis is true]