Question

​Enter all answers to the nearest tenth.

A day care program has an average daily expense of $75.00. The standard deviation is $5.00. The owner takes a sample of 64 bills. What is the probability the mean of his sample will be between $70.00 and $80.00?

Step 1. Calculate a z-score for $70.00 -___
34
1.0
30
68

Step 2. Give the probability for step 1.___%
68
34
1.0
30

Step 3. Calculate the z-score for $80.00 + ___
30
68
1.0
34

Step 4. Give the probability for step 3.___%
30
1.0
68
34

Step 5. Add the probabilities from steps 2&4 . ___%
68
1.0
30
34

Answer 1

Hmm this is a long one give me a sec while i think this out.

Answer 2

Step 1: The formula for Z score is (x - μ) / σ.

x is a raw score to be standardized;
μ is the mean of the population;
σ is the standard deviation of the population.

Therefore the mean is zero. Seventy is -1z, or -1 standard deviation.

Step 2: 34.13% of the cases fall between -1 standard deviation and the mean. Thus there is a 34.13% chance that the score will fall between 70 and 75. This, of course, assumes a normal curve.

Step 3: An 80 is +1z or +1 standard deviation assuming a normal curve.

Step 4: Thirty four percent of the cases fall between +1 standard deviation and the mean. Thus there is a 34.13% chance that the score will fall between 75 and 80. This, of course, assumes a normal curve.

Step 5: Score between +1z and -1z, or +1 and -1 standard deviation account for 68.26% of the cases

Answer 3

There is a detailed explanation :)

Answer 4

thanks