ok the question is..... A random sample of 25 college students has an average test score of 81.5 with a standard deviation of 10.2. The population of test scores is known to be normally distributed. What is the 95% confidence interval for the mean test score of college students?
I know the equation to find the answer is 81.5+/-2.064 *10.2/sqrt25 but how do i get the 2.064
Thank You
2007-10-25 10:20:18 · 1 answers · asked by pickleporkedweasels 1 in Science & Mathematics ➔ Mathematics
The 2.064 comes from the tables for the (Student's) t-distribution. You need to use this because the variance of the population is unknown. The value 2.064 is the entry in the column for 1-alpha = 0.975 (because we put alpha/2 in each tail); and since the sample is of size 25, the number of degrees of freedom is 24.
2007-10-25 10:38:41 · answer #1 · answered by Ron W 7 · 1⤊ 0⤋