(1 point) Consider a normal distribution curve where the middle 45 % of the area under the curve lies above the interval ( 5 , 20 ). Use this information to find the mean, μμ , and the standard deviation, σσ , of the distribution
we know that middle 45% corresponds to z value of 0.5978 (using the standard normal distribution table, it is two sided z critical value)
we have to find the value of and
we can write
setting the z score value, we get
subtracting equation 2 from equation 1,
we get
here will cancel out and using a-(-a) = a+ a = 2a for the standard deviation term, we get
1.1956
dividing both sides by 1.1956, we get
Now, setting the value of standard deviation equation 2 to get the value of mean
we get
adding 7.50239 on both sides, we get
So, the required values are
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