Using the normal distribution, it is found that the life span of an appliance that has a z-score of –3 is of 24 months.
<h3>Normal Probability Distribution</h3>
The z-score of a measure X of a normally distributed variable with mean
and standard deviation
is given by:

- The z-score measures how many standard deviations the measure is above or below the mean.
- Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.
In this problem, the parameters are given as follows:
.
Hence:


X - 48 = -24
X = 24.
The life span of an appliance that has a z-score of –3 is of 24 months.
More can be learned about the normal distribution at brainly.com/question/24663213
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5(9 + 7) = 5 x 9 + 5 x 7 = 45 + 35
Answer:
Mean
Step-by-step explanation:
Given

Required
Best measure of center
The mean is considered the best measure of center when there are no outliers in the given data.
Outlier is when a particular data set is far away from other datasets.
For instance: 20 is an outlier in the following data sets: 
Also, the given data are not open-ended.
An open-ended data is as follows: 
Since we do not have any of the above conditions, then the mean is the best center to use.
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