\begin{tabular}{r|}
9 \\
4 \\
\hline 40 \\
\hline
\end{tabular}

(3) Fifty students were asked to estimate the size of an angle to the nearest degree. Their results, arranged in order of size, are given in Table 14.18.

\begin{tabular}{|llllllllll|}
\hline \multicolumn{8}{|c|}{Estimations (degrees)} \\
\hline 56 & 58 & 58 & 60 & 60 & 61 & 62 & 63 & 64 & 64 \\
65 & 65 & 65 & 66 & 66 & 66 & 66 & 67 & 67 & 68 \\
68 & 68 & 68 & 69 & 69 & 69 & 70 & 70 & 70 & 70 \\
70 & 72 & 72 & 72 & 72 & 73 & 73 & 74 & 74 & 74 \\
75 & 75 & 75 & 76 & 78 & 79 & 80 & 80 & 81 & 83 \\
\hline
\end{tabular}

Table 14.18

a) Construct a frequency distribution table, taking six equal intervals, 55-59, 60-64, [tex][tex]$65-69, \ldots, 80-84$[/tex][/tex].

b) From the frequency distribution table, what is the modal class?



Answer :

Sure, let's go through each part of the question step-by-step.

### Part (a): Frequency Distribution Table

To construct the frequency distribution table, we need to count the number of estimations that fall into each of the specified intervals. The intervals given are 55-59, 60-64, 65-69, 70-74, 75-79, and 80-84.

#### Step-by-step Classification

- Interval 55-59:
- The estimations that fall into this interval are: 56, 58, 58.
- Frequency = 3

- Interval 60-64:
- The estimations that fall into this interval are: 60, 60, 61, 62, 63, 64, 64.
- Frequency = 7

- Interval 65-69:
- The estimations that fall into this interval are: 65, 65, 65, 66, 66, 66, 66, 67, 67, 68, 68, 68, 69, 69, 69.
- Frequency = 15

- Interval 70-74:
- The estimations that fall into this interval are: 70, 70, 70, 70, 72, 72, 72, 72, 73, 73, 74, 74, 74.
- Frequency = 14

- Interval 75-79:
- The estimations that fall into this interval are: 75, 75, 75, 76, 78, 79.
- Frequency = 6

- Interval 80-84:
- The estimations that fall into this interval are: 80, 80, 81, 83.
- Frequency = 4

Using these frequencies, we can construct the frequency distribution table:

[tex]\[ \begin{array}{|c|c|} \hline \text{Interval} & \text{Frequency} \\ \hline 55 - 59 & 3 \\ 60 - 64 & 7 \\ 65 - 69 & 15 \\ 70 - 74 & 14 \\ 75 - 79 & 6 \\ 80 - 84 & 4 \\ \hline \end{array} \][/tex]

### Part (b): Modal Class

The modal class is the interval that has the highest frequency. From our frequency distribution table, we can see:

- Interval 55-59: Frequency = 3
- Interval 60-64: Frequency = 7
- Interval 65-69: Frequency = 15
- Interval 70-74: Frequency = 14
- Interval 75-79: Frequency = 6
- Interval 80-84: Frequency = 4

The interval with the highest frequency is 65-69 with a frequency of 15.

Therefore, the modal class is [tex]\((65, 69)\)[/tex] with a frequency of [tex]\(15\)[/tex].