# Normal Distribution

1. Oct 28, 2012

### emKhairol

1. The problem statement, all variables and given/known data

Question - On a statistics examination, the mean was 78 and the standard deviation was 10. (assume normal distribution).

a) Find the standard scores of two students whose grades were 93 and 62, respectively.

b) Determine the grades of two students whose standard scores were -0.6 and 1.2, respectively.

Informations given :

μ = 78
s = 10

***can you guys help me solving this simple questions seems I really weak in this chapter. Thanks.

2. Relevant equations

$$P (\frac{L-μ}{σ} < Z < \frac{U-μ}{σ})$$

3. The attempt at a solution

So far, I've done half way (I don't know whether is it correct or wrong).

P (L < x < U)
$$P (\frac{L-μ}{σ} < Z < \frac{U-μ}{σ})$$
$$P (\frac{62-78}{10} < Z < \frac{93-78}{10})$$
P (-1.6 < Z < 1.5)

And then, need to draw normal distribution graph. ***I stuck here after find the interval Z values by reading normal distribution table***

Can someone check my answer or perhaps may help me for all the solutions.

Thanks.

2. Oct 28, 2012

### Ray Vickson

It appears that you do not know what a standard score is. I suggest you look in your textbook or course notes, or that you Google 'standard score'.

RGV

3. Oct 28, 2012

### emKhairol

Thanks for your response. I already refer to the text books, notes, and even slides but I still can't catch up with what I learn.