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Answer:
21.77% probability that the proportion who are satisfied with the way that things are going in their life exceeds 0.85
Step-by-step explanation:
Problems of normally distributed samples are solved using the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
For proportions p in a sample of size n, we have that
In this problem:
In a sample of 100 Americans, what is the probability that the proportion who are satisfied with the way that things are going in their life exceeds 0.85
This is 1 subtracted by the pvalue of Z when X = 0.85. So
has a pvalue of 0.7823
1 - 0.7823 = 0.2177
21.77% probability that the proportion who are satisfied with the way that things are going in their life exceeds 0.85