91影视

A frequency distribution is constructed for the number of playing hours.

Refer to Exercise 1CRE; the following frequency distribution is given:

A histogram is a plot that depicts the frequencies of each class interval using adjacent vertical bars.

The length of the bars shows the frequency of the corresponding interval.

The midpoint of any class is obtained by taking the average of the lower and upper limits of the class.

The midpoints of the class intervals are computed below:

$$\begin{gathered} {\text{Midpoint}}_1=\frac{235+239}{2} \\ =237 \\ {\text{Midpoint}}_2=\frac{240+244}{2} \\ =242 \\ {\text{Midpoint}}_3=\frac{245+249}{2} \\ =247 \\ {\text{Midpoint}}_4=\frac{250+254}{2} \\ =252 \\ {\text{Midpoint}}_5=\frac{255+259}{2} \\ =257 \\ {\text{Midpoint}}_6=\frac{260+264}{2} \\ =262 \end{gathered}$$

Use the given steps to construct the histogram:

• Mark the values from 0 up to 9with a gap of 1 unit on the vertical axis.
• Mark the values from 237 to 262 with a gap of 5 units on the horizontal axis.
• Draw vertical bars with a length equal to the given frequency corresponding to each midpoint of equal width.
• Label the horizontal axis as 鈥淭otal Number of Played Hours鈥� and the vertical axis as 鈥淔requency.鈥�

The histogram is constructed as follows:

The following shapes of the histogram depict the corresponding distribution:

• If a histogram is symmetric and bell-shaped, the corresponding distribution is normal.
• If a histogram has flat and even-sized bars, the corresponding distribution is uniform.
• If a histogram has a tail towards the right, the corresponding distribution is skewed to the right.
• If a histogram has a tail towards the left,the corresponding distribution is skewed to the left.

Here, the given histogram appears to be approximately bell-shaped and symmetric.

Thus, it can be said that the distribution is normal.