A group of $600$ job applicants is rated on a scale of $1$ to $50$. The ratings have **mean** $32.5$ and **standard deviation** $7.1$. Approximately how many standard deviations above the mean is a rating of $48$?
AAbout $0.5$ standard deviations above the mean
BAbout $1.0$ standard deviations above the mean
CAbout $2.2$ standard deviations above the mean
DAbout $15.5$ standard deviations above the mean
Answer & Solution
Correct answer: C. About $2.2$ standard deviations above the mean
The number of standard deviations a value $p$ lies from the mean is the **z-score**:
$z = \dfrac{p - \text{mean}}{\text{standard deviation}}$.
For $p = 48$, mean $= 32.5$, SD $= 7.1$:
$z = \dfrac{48 - 32.5}{7.1} = \dfrac{15.5}{7.1} \approx 2.2$.
So $48$ is about $2.2$ standard deviations above the mean.
- Trap A ($0.5$) is the rough z-score for $36$ — a value much closer to the mean.
- Trap B ($1.0$) corresponds to one SD above the mean, which would be $32.5 + 7.1 = 39.6$ — close, but $48$ is further out.
- Trap D ($15.5$) treats the *numerator* as the answer, skipping the division by SD.
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