Answer :
Answer:
Approximately 6 observations are more than 74
Step-by-step explanation:
Problems of normally distributed samples are solved using the z-score formula.
In a set with mean [tex]\mu[/tex] and standard deviation [tex]\sigma[/tex], the zscore of a measure X is given by:
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
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 problem, we have that:
[tex]\mu = 50, \sigma = 12[/tex]
Approximately how many observations are more than 74?
First step is finding the percentage of observations which are higher than 74, which is 1 subtracted by the pvalue of Z when X = 74. So
[tex]Z = \frac{X - \mu}{\sigma}[/tex]
[tex]Z = \frac{74 - 50}{12}[/tex]
[tex]Z = 2[/tex]
[tex]Z = 2[/tex] has a pvalue of 0.9772
1 - 0.9772 = 0.0228
Out of 250
0.0228*250 = 5.7
Approximately 6 observations are more than 74