I have a question regarding confidence intervals as part of a Master's course. The scenario is the following:
In measuring the reaction time of a patient to a certain stimulus, a psychologist estimates the standard deviation as 0.05 seconds. How large a sample of measurements must she take in order to be 95% confident that the error in her estimate of the mean reaction time will not exceed 0.01 seconds?
My thoughts so far are:
Standard deviation = 0.05
Confidence interval = 95%
I am not sure if the NORMSINV() function in Excel could help.
Many thanks in advance.