Question 115 of 480
Given the scores: 4, 7, 8, 11, 13, 8 with corresponding frequencies: 3, 5, 2, 7, 2, 1 respectively. The mean score is
- A. 7.0
- B. 8.7
- C. 9.5
- D. 11.0
Correct Answer:
B
Explanation
To find the mean score given the scores and their corresponding frequencies, we will follow a systematic approach. Let's break it down step-by-step.
### Step 1: Understand the Data
We have two sets of data:
- **Scores**: 4, 7, 8, 11, 13, 8
- **Frequencies**: 3, 5, 2, 7, 2, 1
This means:
- The score of 4 occurs 3 times.
- The score of 7 occurs 5 times.
- The score of 8 occurs 2 times.
- The score of 11 occurs 7 times.
- The score of 13 occurs 2 times.
- The score of 8 occurs again 1 time.
### Step 2: Calculate the Total Score
To find the mean, we first need to calculate the total score by multiplying each score by its frequency and then summing these products.
**Calculations**:
- For score 4: \(4 \times 3 = 12\)
- For score 7: \(7 \times 5 = 35\)
- For score 8 (first occurrence): \(8 \times 2 = 16\)
- For score 11: \(11 \times 7 = 77\)
- For score 13: \(13 \times 2 = 26\)
- For score 8 (second occurrence): \(8 \times 1 = 8\)
Now, we sum these products:
\[
\text{Total Score} = 12 + 35 + 16 + 77 + 26 + 8 = 174
\]
### Step 3: Calculate the Total Frequency
Next, we need to calculate the total frequency by summing all the frequencies:
\[
\text{Total Frequency} = 3 + 5 + 2 + 7 + 2 + 1 = 20
\]
### Step 4: Calculate the Mean
The mean is calculated using the formula:
\[
\text{Mean} = \frac{\text{Total Score}}{\text{Total Frequency}}
\]
Substituting the values we calculated:
\[
\text{Mean} = \frac{174}{20} = 8.7
\]
### Conclusion
Thus, the mean score is **8.7**, which corresponds to option **B**.
### Explanation of Other Options
- **Option A (7.0)**: This is incorrect because it underestimates the total score based on the frequencies provided.
- **Option C (9.5)**: This option is also incorrect as it suggests a higher mean than what the calculations show. It may arise from miscalculating the total score or frequency.
- **Option D (11.0)**: This option is incorrect as it implies a mean that is higher than the highest score weighted by its frequency, which is not possible.
### Revision Summary
- The mean is calculated by dividing the total score by the total frequency.
- Always multiply each score by its frequency before summing to find the total score.
- Ensure to sum all frequencies accurately to avoid errors in the mean calculation.
- The correct mean score for the given data is **8.7** (Option B).