In: Statistics and Probability
Use the normal distribution of SAT critical reading scores for which the mean is 509 and the standard deviation is 121. Assume the variable x is normally distributed. left parenthesis a right parenthesis What percent of the SAT verbal scores are less than 650? left parenthesis b right parenthesis If 1000 SAT verbal scores are randomly selected, about how many would you expect to be greater than 550?
X ~ Normal(509,1212)
(a)
The following information has been provided:
μ=509, σ=121
We need to compute Pr(X≤650). The corresponding z-value needed to be computed:
Therefore,
The following is obtained graphically:
(b)
The following information has been provided:
μ=509, σ=121
We need to compute Pr(X≥550). The corresponding z-value needed to be computed is:
Therefore, we get that
The following is obtained graphically:
Out of 1000, we would expect 1000*0.3674 = 367 to have scores greater than 550.
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