The annua water bills for households Enter End 0 Del ins 2. (2 points) The annua

Question

The annua water bills for households Enter End 0 Del ins 2. (2 points) The annual water bills for all households in a large city are normally distributed with a mean of $480 and standard deviation of $100. (a) Find the probability of selecting a household whose annual water bill is less than $450. (b) Find the probability of selecting a random sample of 50 households whose mean annual water bill is less than $450. x450)OD 3. (2 points) Fifteen fourth-grade students were randomly assigned to three groups to exper- ment with three different methods of teaching arithmetic. At the end of the semester, the same test was given to all 15 students. The table gives the scores of the students in the three ther the mean score is the same for all three

Explanation / Answer

A) P(X < 450) = P((X - mean)/SD < (450 - 480)/100)

= P(Z < -0.3)

= 0.3821

B) P(X < 450) = P((x - mean)/(SD/sqrt (n )) < (450 - 480)/(100/sqrt(50))

= P(Z < -2.12)

= 0.0170

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