for 99% CI
|
for 99 % CI value of z= |
2.576 |
|
standard deviation ?= |
12.40 |
|
margin of error E = |
3 |
| required
sample size
n=(z?/E)2
= |
114.0 |
for 95% CI:
|
for 95 % CI value of z= |
1.960 |
|
standard deviation ?= |
12.40 |
|
margin of error E = |
3 |
| required
sample size
n=(z?/E)2
= |
66.0 |
from above:
A? 99% confidence level requires 114
subjects
A 95 % confidence level requires 66
subjects.
C. Decreasing the confidence level decreases the sample
size needed.
