In: Statistics and Probability
Use a normal approximation to find the probability of the indicated number of voters. In this case, assume that 156 eligible voters aged 18-24 are randomly selected. Suppose a previous study showed that among eligible voters aged 18-24, 22% of them voted.
The probability that fewer than 37 voted
The following information has been provided about the population proportiona and the sample size:
| Population Proportion = | 0.22 |
| Sample Size = | 156 |
We need to compute
.
Based on the information provided, the population men of sample
proportions and the corresponding standard error are:


Observe that:

which indicates that the assumption for normal approximation for the sampling distribution is met.
Since we need to use a continuity correction, we need to use the factor
to adjust the end points of the end points of the probability
intervals, so the new limits are:


Now, the following is obtained using normal approximation:

Therefore, based on the information provided, it is concluded that

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