MS 150 Statistics Fall 2002 Quiz Nine: 9.4

Science courses at the national campus Fall 2001 and Spring 2002 had an overall mean grade = 2.103

Five hundred and eight (508) female students in science courses at the national campus Fall 2001 and Spring 2002 had a mean grade point x = 2.000 with a standard deviation sx = 1.221. At an alpha a = 0.05, is the female student mean grade point statistically significantly different than the overall mean grade point in science courses at the national campus Fall 2001 and Spring 2002? Use a two-tailed test.

  1. What is the null hypothesis?
  2. What is the alternate hypothesis?
  3. What is a?
  4. Determine tc
  5. Find the t-statistic t
  6. Make a sketch of the t-distribution including the tails, tc, and the t-statistic.
  7. Do we:
    1. Reject the null hypotheis OR
    2. Fail to reject the null hypothesis?
  8. Is the female students mean grade point in science courses at the national campus significantly different from the overall mean grade point at an alpha of 0.05?
  9. What is the p-value for this hypothesis test?
  10. What is the smallest alpha a for which the t-statistic is significant?
Statistic or Parameter Symbol Equations Excel
Confidence interval statistics
Degrees of freedom df = n-1 =COUNT(data)-1
Hypothesis Testing
Calculate a t-statistic t t xbartot.gif (1028 bytes)
Calculate t-critical for a two-tailed test tc =TINV(a,df)
Calculate a p-value from a t-statistic (2 tail) p = TDIST(ABS(tstat),df,2)