MS 150 Statistics Quiz 07 Fall 2003 8.1 • Name: _______________
Over a sample size n of 30 weeks the cafeteria found that they have been using
a sample mean x
of 22.5 bags of rice per week with a sample standard deviation sx of 2.5. Construct a 95% confidence interval for the population mean number of rice bags.
- _______ Write down the sample size n.
- _______ Is the sample size n greater than or equal to 30?
- _______ Write down the sample sample mean
x.
- _______ Write down the sample standard deviation sx.
- _______ Write down the confidence level c.
- Use the information above to sketch the 95% confidence interval:
- _______ Determine the area in both tails.
- _______ Determine the area in the left tail.
- _______ Determine the left -zc value.
- _______ Write down the right zc value.
- _______ Determine the error E.
- _______ Determine the left (lower) bound for the population mean µ.
- _______ Determine the right (upper) bound for the population mean µ.
- The confidence interval for the population mean number of rice bags µ is:
_________ < µ < _________
Confidence interval statistics |
Find a zc value from a confidence level c |
zc |
|
=ABS(NORMSINV((1-c)/2)) |
Calculate an error tolerance E of a mean for n >= 30 using
sx |
E |
|
=zc*sx/SQRT(n) |
Calculate a confidence interval for a population mean µ from
a sample mean x and an error tolerance E |
|
x-E<= µ
<=x+E |
|