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The following table gives the frequency distribution of the scores obtained in a dictation test by a group of students in a class. Calculate the mean, median, and mode.

\begin{tabular}{c|c}
Marks & Frequency \\
\hline
[tex]$0-4$[/tex] & 1 \\
[tex]$5-9$[/tex] & 5 \\
[tex]$10-14$[/tex] & 7 \\
[tex]$15-19$[/tex] & 13 \\
[tex]$20-24$[/tex] & 11 \\
[tex]$25-29$[/tex] & 9 \\
\end{tabular}


Sagot :

To determine the mean scores from the given frequency distribution of scores, let's proceed step-by-step.

Here is the given frequency distribution:

[tex]\[ \begin{array}{|c|c|} \hline \text{Mark Interval} & \text{Frequency} \\ \hline 0-4 & 1 \\ 5-9 & 5 \\ 10-14 & 7 \\ 15-19 & 13 \\ 20-24 & 11 \\ 25-29 & 9 \\ \hline \end{array} \][/tex]

### Step 1: Calculate Mid-Points of Each Interval

First, we need to find the mid-point for each class interval. The mid-point can be found by averaging the lower and upper bounds of each interval.

- For the interval [tex]\(0-4\)[/tex]:
[tex]\[ \frac{0+4}{2} = 2 \][/tex]

- For the interval [tex]\(5-9\)[/tex]:
[tex]\[ \frac{5+9}{2} = 7 \][/tex]

- For the interval [tex]\(10-14\)[/tex]:
[tex]\[ \frac{10+14}{2} = 12 \][/tex]

- For the interval [tex]\(15-19\)[/tex]:
[tex]\[ \frac{15+19}{2} = 17 \][/tex]

- For the interval [tex]\(20-24\)[/tex]:
[tex]\[ \frac{20+24}{2} = 22 \][/tex]

- For the interval [tex]\(25-29\)[/tex]:
[tex]\[ \frac{25+29}{2} = 27 \][/tex]

### Step 2: List Mid-Points and Frequencies

| Interval | Mid-point ([tex]\(x_i\)[/tex]) | Frequency ([tex]\(f_i\)[/tex]) |
|----------|---------------------|---------------------|
| 0-4 | 2 | 1 |
| 5-9 | 7 | 5 |
| 10-14 | 12 | 7 |
| 15-19 | 17 | 13 |
| 20-24 | 22 | 11 |
| 25-29 | 27 | 9 |

### Step 3: Calculate [tex]\( f_i \cdot x_i \)[/tex]

Next, calculate the product of each frequency and its corresponding mid-point.

| Interval | Mid-point ([tex]\(x_i\)[/tex]) | Frequency ([tex]\(f_i\)[/tex]) | [tex]\(f_i \cdot x_i\)[/tex] |
|----------|---------------------|---------------------|---------------------|
| 0-4 | 2 | 1 | 2 |
| 5-9 | 7 | 5 | 35 |
| 10-14 | 12 | 7 | 84 |
| 15-19 | 17 | 13 | 221 |
| 20-24 | 22 | 11 | 242 |
| 25-29 | 27 | 9 | 243 |

### Step 4: Find the Sum of Frequencies and Sum of [tex]\( f_i \cdot x_i \)[/tex]

Sum of frequencies ([tex]\(\sum f_i\)[/tex]):
[tex]\[ 1 + 5 + 7 + 13 + 11 + 9 = 46 \][/tex]

Sum of the products ([tex]\(\sum f_i \cdot x_i\)[/tex]):
[tex]\[ 2 + 35 + 84 + 221 + 242 + 243 = 827 \][/tex]

### Step 5: Calculate the Mean

Now, divide the sum of the products by the sum of the frequencies to find the mean:

[tex]\[ \text{Mean} = \frac{\sum f_i \cdot x_i}{\sum f_i} = \frac{827}{46} \approx 17.978 \][/tex]

So, the mean score is approximately [tex]\( 17.978 \)[/tex].