Reference no: EM13266198

Assignment 3: Sample Size

For this assignment you will be provided with 2 clinical research questions on sample size and one published paper to determine the power of the primary outcome measure reported in the study.

Situation 1: Sample Size

A survey is being planned to estimate the prevalence of secondary infertility amongst couples aged 20-45. The investigators expect the prevalence to be 10%, and would like to estimate it to within 5% of the true value (with 90% confidence). How many couples are required? 

Situation 2: Sample Size

A previous small study was investigating the total cost of 10 specific items of fruits and vegetables which were sold in 3 supermarkets compared to that were sold in 3 local corner shops.  On average the total cost of 10 specific items of fruits and vegetables which were sold in local corner shops was £5.50. It was suggested that the total cost of those fruits and vegetables which were sold in supermarkets was 50% cheaper than the local corner shops, with a common standard deviation of 1.65. Use the PS power calculator to find out how many supermarkets and local corner shops are required (assume equal group) , if we are going to conduct a similar study to investigate the difference in cost of this size, with 90% power and using a 1% significance level?

Situation 3: 

Read the paper titled “Plasma Fetuin –A is associated with the Severity and Cognitive Impairment in Mild to moderate Alzheimer’s Disease” Edward R. Smith, RaminNilforooshan et al. Journal of Alzheimer’s disease, 2010

Identify the primary outcome measure and calculate using PS-sample size program to determine the power of the primary outcome measure, stating clearly the measures that were used to arrive at the result. Use 0.05 as type I error for the calculation. Also comment on the value of the difference whether this was clinically relevant or not.