Corrected Mean 309E95
1. **State the problem:**
We have a dataset of 200 items with an initial mean of 80. Two items were recorded incorrectly: 61 was recorded as 16, and 45 was recorded as 15. We need to find the corrected mean.
2. **Recall the formula for mean:**
The mean $\bar{x}$ is given by
$$\bar{x} = \frac{\text{sum of all items}}{N}$$
where $N$ is the number of items.
3. **Calculate the original total sum:**
Given the mean $\bar{x} = 80$ and $N = 200$, the total sum of all items is
$$\text{sum} = \bar{x} \times N = 80 \times 200 = 16000$$
4. **Adjust the sum for the incorrect entries:**
The incorrect sum includes 16 and 15 instead of 61 and 45. So, the sum was underestimated by
$$ (61 - 16) + (45 - 15) = 45 + 30 = 75 $$
5. **Calculate the corrected sum:**
$$\text{corrected sum} = 16000 + 75 = 16075$$
6. **Calculate the corrected mean:**
$$\text{corrected mean} = \frac{\text{corrected sum}}{N} = \frac{16075}{200} = 80.375$$
**Final answer:** The corrected mean is $80.375$.