Math Problem Statement
The national average for mathematics SATs in 2011 was 514. Suppose that the distribution of scores was approximately bell-shaped and that the standard deviation was approximately 40. Within what boundaries would you expect 68% of the scores to fall? What percentage of scores would be above 594?
Solution
We are given that the SAT scores follow a bell-shaped (normal) distribution with:
- Mean (μ) = 514
- Standard deviation (σ) = 40
Part 1: Boundaries for 68% of the Scores
According to the Empirical Rule for normal distributions:
- 68% of the data falls within one standard deviation of the mean, which means between and .
Thus, the boundaries are:
Therefore, 68% of the SAT scores would fall between 474 and 554.
Part 2: Percentage of Scores Above 594
First, we calculate how many standard deviations 594 is from the mean. This is done using the z-score formula: Where:
Substitute the values: So, a score of 594 is 2 standard deviations above the mean.
Using the standard normal distribution table, a z-score of 2 corresponds to approximately 97.72% of the data lying below this value. Hence, the percentage of scores above 594 is:
Thus, approximately 2.28% of the scores would be above 594.
Let me know if you would like further details or have any questions.
Here are 5 related questions to explore:
- What percentage of scores would be below 434?
- What percentage of scores would fall between 474 and 594?
- How would the boundaries change if the standard deviation were 50 instead of 40?
- What is the z-score for a score of 454?
- What is the probability of getting a score below 474?
Tip: The empirical rule is a quick way to estimate percentages in a normal distribution, but for more precision, use z-scores and normal distribution tables.
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Math Problem Analysis
Mathematical Concepts
Statistics
Normal Distribution
Empirical Rule
Z-Score
Formulas
Empirical Rule: 68% of data lies within one standard deviation of the mean
Z-Score Formula: z = (x - μ) / σ
Theorems
Empirical Rule
Properties of Normal Distribution
Suitable Grade Level
Grades 10-12