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#6**+10 **

9a. Doesn't specify if 1-sided or 2-sided required (perhaps appendix F only has one set of values - don't know as we can't see it!).

There are a set of t-tables online at https://www.easycalculation.com/statistics/t-distribution-critical-value-table.php

Here is an extract:

I've ringed both the 1 and 2 tail values for degrees of freedom 11 (sample size - 1) for 95% confidence

(α = 1 - 95/100).

.

Alan Dec 9, 2014

#2**+10 **

Q13

I am feeling my way here - this is not my area.

The population has a mean for 60 and a standard deviation of 12

you take a sample of 9 from this population

The mean of all samples of 9 is still 60

However the standard error for samples means for your sample of 9 is $$\sigma_{\bar x}=\frac{\sigma}{\sqrt n}=\frac{12}{\sqrt 9}=4$$

You need to find Z scores for the sample means of 63 and 56

$$\\ Z=\frac{X-\mu_{\bar x}}{\sigma_{\bar x}}\\\\

when \;X=63\\\\

Z=\frac{63-60}{4}\\\\

Z=0.75\\

-------------------\\

when \;X=56\\\\

Z=\frac{56-60}{4}\\\\

Z=-1\\

--------------------\\$$

NOW I used this wonderful site that I expect I got from Geno

http://davidmlane.com/hyperstat/z_table.html

(I could have used this site to finish without finiding the z scores first)

Prob that the mean of the sample is greater than 63 is 0.2266

Prob that the mean of the sample is less than 56 is 0.1587

Prob that the mean of the sample is between 56 is 63 is 0.6147

check

$${\mathtt{0.226\: \!6}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.158\: \!7}}{\mathtt{\,\small\textbf+\,}}{\mathtt{0.614\: \!7}} = {\mathtt{1}}$$ Good that is what it had to add up to :)

I think that is correct

Melody Dec 7, 2014

#4**+5 **

There is no question for 16

and

I am not too sure about the other 2.

I am pretty sure my first answer is correct.

Melody Dec 8, 2014

#6**+10 **

Best Answer

9a. Doesn't specify if 1-sided or 2-sided required (perhaps appendix F only has one set of values - don't know as we can't see it!).

There are a set of t-tables online at https://www.easycalculation.com/statistics/t-distribution-critical-value-table.php

Here is an extract:

I've ringed both the 1 and 2 tail values for degrees of freedom 11 (sample size - 1) for 95% confidence

(α = 1 - 95/100).

.

Alan Dec 9, 2014