Suppose that a Normal model describes the acidity (pH) of rainwater, and that water tested after last week's storm had a z-score of 1.8.This means that the acidity of that rain …
A) varied with a standard deviation of $1.8$.
B) had a pH $1.8$ higher than average rainfall.
C) had a pH $1.8$ standard deviations higher than that of average rainwater.
D) had a $\mathrm { pH }$ of $1.8$.
E) had a pH $1.8$ times that of average rainwater.

Question

Suppose that a Normal model describes the acidity (pH) of rainwater, and that water tested after last week's storm had a z-score of 1.8.This means that the acidity of that rain … 
A) varied with a standard deviation of $1.8$.
B) had a pH $1.8$ higher than average rainfall.
C) had a pH $1.8$ standard deviations higher than that of average rainwater.
D) had a $\mathrm { pH }$ of $1.8$.
E) had a pH $1.8$ times that of average rainwater.

Quizplus · Accepted Answer

A z-score represents the number of standard deviations a data point is from the mean. Therefore, a z-score of 1.8 indicates the rainwater's acidity was 1.8 standard deviations higher than the average.

Suppose That a Normal Model Describes the Acidity (PH) of Rainwater