Question

Jeff and his friends took some intelligence drugs from some website. They all did an IQ test after and wanted to see if their scores are significantly affected by the drug They know that the population mean for IQ is 100.

Here are their scores: 90, 100, 105, 110, 80

their mean=97

mean of the population =100

n=5

df=5-1 =4

s=12.042

97-100/12.042/square root*5 =-.0.557

t(4) =2.776

Since it is less than critical t value, we fail to reject the null hypotheses. My question is how do you calculate the effect size through cohen's d?

Answer 1

Jeff and his friends took some intelligence drugs from some website. They all did an IQ test after and wanted to see if their scores are significantly affected by the drug They know that the population mean for IQ is 100.

Here are their scores: 90, 100, 105, 110, 80

their mean=97

mean of the population =100

n=5

df=5-1 =4

s=12.042

97-100/12.042/square root*5 =-.0.557

t(4) =2.776

Since it is less than critical t value, we fail to reject the null hypotheses. My question is how do you calculate the effect size through cohen's d?

cohen's d is calculated as the difference between the mean of the data and µ divided by the standard deviation of the data. = (|mean-µ|)/s

cohen's d =(|97-100|)/12.042

= 0.2491

The effect size is small.