# Need help with business stat

#### summer stat

##### New Member

1. Suppose you have selected a random sample of n+5 measurements from a normal distribution. Compare the standard normal Z values with the corresponding t-values if you were forming the following confidence intervals.
a. 80% confidence interval
b. 90% confidence interval
c. 95% confidence interval
d. 98% confidence interval
e. 99% confidence interval
f. use the table values you obtained in parts a-e to sketch the z- and t- distributions. What are the similarities and differences?

2. Periodically the Hillsboruogh County(Florida) Water department tests the drinking water of homeowners for contaminants such as lead and cooper. The lead and copper levels in water specimens collected for a sample of 10 residents of the crystal lake manors subdivision are shown below

1.32
0
13.1
.919
.657
3.0
1.32
4.09
4.45
0 .743

Copper (MG/L)
.508
.279
.320
.904
.221
.283
.475
.130
.220
.743

a. construct a 99% confidence interval for the mean lead level in water specimens from Crystal Lakes Manors

b. construct a 99%% confidence interval for the mean copper level in water specimens from crystal lakes manors

c. Interpret the intervals, parts a and b, in the words of the problem

d. discuss the meaning of the phrase, "99% confident".