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IQ scores are normally distributed with a mean of 100 and a standard deviation of 15.
Out of a randomly selected 2200 people from the population, how many of them
would have an IQ less than 115, to the nearest whole number?


Sagot :

Using the normal distribution, it is found that 1851 people would have an IQ less than 115.

Normal Probability Distribution

The z-score of a measure X of a normally distributed variable with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex] is given by:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

  • The z-score measures how many standard deviations the measure is above or below the mean.
  • Looking at the z-score table, the p-value associated with this z-score is found, which is the percentile of X.

The mean and the standard deviation are given, respectively, by:

[tex]\mu = 100, \sigma = 15[/tex]

The proportion of IQ scores less than 115 is the p-value of Z when X = 115, hence:

[tex]Z = \frac{X - \mu}{\sigma}[/tex]

[tex]Z = \frac{115 - 100}{15}[/tex]

Z = 1

Z = 1 has a p-value of 0.8413.

Out of 2200 people:

0.8413 x 2200 = 1851.

More can be learned about the normal distribution at https://brainly.com/question/27643290

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