AcaStat Statistical Software

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Contents  Introduction Descriptive Hypothesis Tables Appendix

Example: Interval Estimation for Means
 

Problem: A random sample of 30 incoming college freshmen revealed the following statistics: mean age 19.5 years; standard deviation 1.2. Based on a 5% chance of error, estimate the range of possible mean ages for all incoming college freshmen.

Estimation

Critical value (CV)

Df=n-1 or 29

Consult t-distribution for alpha .05, 2-tailed

 CV=2.045 Standard error

Estimate

or 

Interpretation We are 95% confident that the actual mean age of the all incoming freshmen will be somewhere between 19 years (the lower limit) and 20 years (the upper limit) of age.