Answer:
The sample size needed is 2401.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of
, and a confidence level of
, we have the following confidence interval of proportions.

In which
z is the zscore that has a pvalue of
.
The margin of error of the interval is:

95% confidence level
So
, z is the value of Z that has a pvalue of
, so
.
Estimate the sample size needed if no estimate of p is available so that the confidence interval will have a margin of error of 0.02.
We have to find n, for which M = 0.02.
There is no estimate of p available, so we use 






The sample size needed is 2401.
Answer:
The value is 
Step-by-step explanation:
From the question we are told that
The sample size is n = 20
The sample mean is 
The standard deviation is 
Generally the standard error of the mean is mathematically represented as

=> 
=> 
25/12.5 = 40/y
cross multiply
(25)(y) = (12.5)(40)
25y = 500
y = 500/25
y = 20 <====