The base 10 logarithm of 55 cycles-to-failure observations on specimens subjected to a constant stress level in

Question:

The base 10 logarithm of 55 cycles-to-failure observations on specimens subjected to a constant stress level in fatigue have been classified as follows:

Here y is the class midpoint and f is the class frequency.
(a) Estimate the mean and standard deviation of the population from which the sample was taken and establish the normal PDF.
(b) Plot the histogram and superpose the predicted class frequency from the normal fit.