Consider a Set of 50 Measurements with a Mean of 50.2

Essay

Consider a set of 50 measurements with a mean of 50.2 and a standard deviation of 18.7 and with the following observed and expected frequencies. $$\begin{array} { l c c } \text { Interval } & \text { Observed Frequencies } & \text { Expected frequencies } \\39.99 \text { and less } & 12 & 14.56 \\40 - 59.99 & 18 & 20.365 \\60 - 79.99 & 15 & 12.28 \\80 \text {-and higher } & 5 & 2.795\end{array}$$ It is desired to test whether these measurements came from a normal population.
-Calculate the value of the chi-square test statistic?