MS 150 Statistics Quiz 08 Fall 2004 9.2 • Name: _______________

A sample size n of 19 female students in MS 150 statistics spring 2005 had their body fat measured. The sample mean body fat x is 30.16 with a sample standard deviation sx of 9.54. Construct a 95% confidence interval for a population mean female body fat among females students at the national campus. Note that n ≤ 30.

  1. confidence level: c = ______________
  2. degrees of freedom: = ______________
  3. t-critical: tc = ______________
  4. Error tolerance E: = ______________
  5. The confidence interval for the population mean female body fat is:

    P( _________ ≤ ≤ _________ ) = 0.95
  6. _______ Based on the sample, could the population mean female body fat be above 33%, the lower limit for being overfat, at a 95% confidence level?

normal curve

Confidence interval statistics
Find a tc value from a confidence level c and sample size n tc   =TINV(1-c,n-1)
Calculate an error tolerance E of a mean for any n ≥ 5 using sx. E error_tolerance_tc.gif (989 bytes) =tc*sx/SQRT(n)
Calculate a confidence interval for a population mean from a sample mean x and an error tolerance E   x-E≤ ≤x+E