The '68-95-99.7' rule says
-About 68% of values fall within one standard deviation of the mean.
-About 95% of the values fall within two standard deviations from the mean.
-Almost all of the values — about 99.7% — fall within three standard deviations from the mean.
Here
Therefore, the probability
The required probability
The mean of this test will be 57.
<h3>What is Standard Deviation and Mean?</h3>
A standard deviation (or σ) is a measure of how dispersed the data is in relation to the mean.
The mean can be used to get an overall idea, or picture, of the data set.
Let Mean be 'm'
and standard deviation=
So, m-2=49
and, m + =61
Solving the above two equation we get
Now, m= 61-
= 61-4
= 57
So , the mean of this test will be =57
Learn more about mean and standard deviation here:
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