# Probability of Sampling Error Assistance

#### heidir1224

##### New Member
Hello! I am working on a mini project and am stuck on the third question! I think it's how the question is phrased that is throwing me off..?

I have posted the first two questions as well to see if that is somehow impacting my answer?

1. Compute the sample mean x and the sample standard deviation sx of Albertson’s grocery prices.
a. x=3.862
b. Sx = 1.1599
2. State the population mean µx and population standard deviation σx of sample mean x in terms of population mean µx and population standard deviation σx for the original variable x. (Hint: You don’t need to compute anything here. Think back to chapter 6)
a. µx = 3.862
b. σx = 1.1599
3. Find the probability that sampling error made in estimating the mean Albertson’s grocery prices is $0.50 or less. (For this problem, assume that the standard deviation σx is known to be$ 1.10).
a.
P(Sampling Error <.50)
Z=(x-µ )÷ ( σ÷√(n)
Z = (4.362 – 3.862) ÷ (1.1599 ÷ √25)
Z = .50 ÷ .23198
Z = 2.155358

I looked up 2.15 on the z-table and got .4842 which is 48.42%. Is this at all in the ball park? I feel like it's completely wrong and not what he's looking for.

Any and all help would be greatly appreciated! :tup:

Data:
3.29
4.99
3.49
3.49
3.89
3.69
3.99
1.99
2.99
4.99
3.29
2.79
4.39
3.29
3.59
6.99
2.99
3.69
3.29
3.19
4.99
2.99
6.69
4.59
2.99