for 99% confidence interval:
|
for 99 % CI value of z= |
2.576 |
|
standard deviation σ= |
12.50 |
|
margin of error E = |
3 |
|
required sample size
n=(zσ/E)2                                       Â
= |
116.0 |
for 90% confidence interval:
|
for 90 % CI value of z= |
1.645 |
|
standard deviation σ= |
12.50 |
|
margin of error E = |
3 |
| required
sample size
n=(zσ/E)2                                       Â
= |
47.0 |
hence decreasing  confidence interval to 90% will
decrease the requirement of sample size.
