Suppose that the mean and standard deviation of the scores in a Statistics exam are 75 and 9.5 respectively. What minimum score
1 answer:
The mean and standard deviation of the scores are 75 and 9.5 respectively.
The z-score is a means to find the probability of getting a particular score. This is calculated to be:
where x is the score, μ is the mean, and σ is the standard deviation.
To be a part of the top 2.5 percent, the probability is:
The z-score for this probability, that is, P
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. Multiplying the denominator by
gives
Subtracting this from the numerator gives a remainder of
. Multiplying the denominator by
gives
and subtracting this from the previous remainder gives a new remainder of
This last remainder is exactly the same as the denominator, so divides through it exactly and leaves us with 1.
What we showed here is that
and this last expression is the quotient.
To verify this solution, we can simply multiply this by the original denominator:
which matches the original numerator.