A person must score in the upper 2% of the population on an IQ test to qualify for membership in Mensa, the international high-IQ society. If IQ scores are normally distributed with a mean of 100 and a standard deviation of 15, what score must a person have to qualify for Mensa (to whole number)?

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**Question:**

A person must score in the upper 2% of the population on an IQ test to qualify for membership in Mensa, the international high-IQ society. If IQ scores are normally distributed with a mean of 100 and a standard deviation of 15, what score must a person have to qualify for Mensa (to whole number)?

**Explanation:**

To solve this problem, we need to determine what IQ score corresponds to the top 2% of the distribution. We have:

- Mean (μ) = 100
- Standard Deviation (σ) = 15

For a normal distribution, the Z-score formula is:

\[ Z = \frac{(X - μ)}{σ} \]

Where \( X \) is the score we are trying to find.

For the top 2%, we look for the Z-score that corresponds to the 98th percentile (as 100% - 2% = 98%).

Using a Z-table or calculator, you find that the Z-score corresponding to the 98th percentile is approximately 2.05.

Now, use the Z-score formula to solve for \( X \):

\[ 2.05 = \frac{(X - 100)}{15} \]

Solving for \( X \):

\[ X - 100 = 2.05 \times 15 \]
\[ X - 100 = 30.75 \]
\[ X = 130.75 \]

Therefore, a person must score approximately 131 to qualify for Mensa.
Transcribed Image Text:**Question:** A person must score in the upper 2% of the population on an IQ test to qualify for membership in Mensa, the international high-IQ society. If IQ scores are normally distributed with a mean of 100 and a standard deviation of 15, what score must a person have to qualify for Mensa (to whole number)? **Explanation:** To solve this problem, we need to determine what IQ score corresponds to the top 2% of the distribution. We have: - Mean (μ) = 100 - Standard Deviation (σ) = 15 For a normal distribution, the Z-score formula is: \[ Z = \frac{(X - μ)}{σ} \] Where \( X \) is the score we are trying to find. For the top 2%, we look for the Z-score that corresponds to the 98th percentile (as 100% - 2% = 98%). Using a Z-table or calculator, you find that the Z-score corresponding to the 98th percentile is approximately 2.05. Now, use the Z-score formula to solve for \( X \): \[ 2.05 = \frac{(X - 100)}{15} \] Solving for \( X \): \[ X - 100 = 2.05 \times 15 \] \[ X - 100 = 30.75 \] \[ X = 130.75 \] Therefore, a person must score approximately 131 to qualify for Mensa.
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