Science Buddies: "Ask an Expert"

Hey...

I am having trouble calculating the Standard Error and Critical Ratio for my project...(Testing for Bias in a Photo Lineup). I had 12 Mock Witnesses, and the proportions are 0.583 chose the suspect, and 0.417 chose the fillers. Can someone help me calculate them? Thanks!

* Please respond as soon as possible.

Hello Isabelyarb,

The standard error equation- s/n^.5 , applies mainly to calculating standard deviation of the sampling distribution of the mean. Since you are using proportions, this formula will not work. Instead you can use this equation to calculate the standard deviation of the sampling distribution of a proportion- (p*(1-p)/n)^.5. However your experiment results display a population distribution rather than a sampling distribution. A sampling distribution is defined as the distribution of all possible samples of size n from a population.

Good Luck and let me know if you have more questions,

C.M.