Assume that z is the test statistic. (Give your answers correct to two decimal places.)

(d) Calculate the value of z for Ho: ì = 81, ó = 13.3, n = 51, x = 79.7.
-1.16 is my answer and it is wrong, can someone tell me how I missed this one, done several and got them right but not this one.

Yes. your anwser is wrong.

In case you think I did not work it and just put a number down I worked it like this 79.7-81 over 13.3sqrt 51=-1.3/1.8623 so did I put the formula in wrong or what, I got all the other ones right with this formula?

z= (79.7- 81)/(13.3/sqrt(51))

z= -1.3/1.862372512

z = -0 .698 or -0.70

Thank you, I am not sure how my calculator came up with that answer. But I had worked it out like you did.

because you multiply 13.3 sqrt (51) but it is division. 13.3/sqrt(51).

To calculate the value of the test statistic (z), you need to use the formula:

z = (x - μ) / (σ / √n)

where:
x is the sample mean,
μ is the population mean,
σ is the population standard deviation,
n is the sample size.

In this case, you have:
x = 79.7
μ = 81
σ = 13.3
n = 51

Plugging in these values, we can calculate the z statistic as follows:

z = (79.7 - 81) / (13.3 / √51)
z = -1.3 / (13.3 / 7.14)
z ≈ -1.3 / 1.86
z ≈ -0.70

Rounded to two decimal places, the value of z is approximately -0.70.

It seems like you might have made a calculation error when computing the value of σ / √n. Make sure to divide the standard deviation (σ) by the square root of the sample size (√n) to get the correct result.