normally distributed score have mean 100 and standard deviation 15. use the standard z-table to the following; probability of randomly selecting someone with score less than 80, greater than 136 and between 95 and 110
Question
normally distributed score have mean 100 and standard deviation 15. use the standard z-table to the following; probability of randomly selecting someone with score less than 80, greater than 136 and between 95 and 110
Solution
To answer this question, we need to convert the scores to z-scores and then use the standard z-table to find the probabilities.
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Probability of randomly selecting someone with a score less than 80:
Z = (X - μ) / σ = (80 - 100) / 15 = -1.33
Looking up this z-score in the z-table, we find a probability of 0.0918. So, the probability of randomly selecting someone with a score less than 80 is 0.0918 or 9.18%.
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Probability of randomly selecting someone with a score greater than 136:
Z = (X - μ) / σ = (136 - 100) / 15 = 2.4
Looking up this z-score in the z-table, we find a probability of 0.9918. However, since we want the probability of a score greater than 136, we need to subtract this value from 1. So, the probability is 1 - 0.9918 = 0.0082 or 0.82%.
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Probability of randomly selecting someone with a score between 95 and 110:
For X = 95, Z = (95 - 100) / 15 = -0.33. The corresponding probability from the z-table is 0.3707.
For X = 110, Z = (110 - 100) / 15 = 0.67. The corresponding probability from the z-table is 0.7486.
To find the probability of a score between 95 and 110, subtract the smaller probability from the larger one: 0.7486 - 0.3707 = 0.3779 or 37.79%.
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