Answer:
a) 0.7734
Step-by-step explanation:
Problems of normal distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
In this question, we have that:
(a) what proportion of children aged 13 to 15 years old have scores on this test above 83 ?
This is 1 subtracted by the pvalue of Z when X = 83. So
has a pvalue of 0.2266
1 - 0.2266 = 0.7734
The answer is 0.7734