# how did they get this?

• Jun 8th 2008, 08:42 PM
crashuk
how did they get this?
mean=1.5 standard deviation=10 n=20 sample mean=1.2

1.2-1.5 = 1.3 10/4.47213 =2.236 1.3/2.236= -0.134
p value= .3669?

but i get .4483
• Jun 8th 2008, 08:45 PM
CaptainBlack
Quote:

Originally Posted by crashuk
mean=1.5 standard deviation=10 n=20 sample mean=1.2

1.2-1.5 = 1.3 10/4.47213 =2.236 1.3/2.236= -0.134
p value= .3669?

but i get .4483

But consider looking your value up in a table of the t-distribution with 19 degrees of freedom rather than the normal table.

RonL
• Jun 8th 2008, 09:28 PM
crashuk
Quote:

Originally Posted by CaptainBlack

But consider looking your value up in a table of the t-distribution with 19 degrees of freedom rather than the normal table.

RonL

thats all that was given
• Jun 8th 2008, 10:50 PM
mr fantastic
Quote:

Originally Posted by crashuk
mean=1.5 standard deviation=10 n=20 sample mean=1.2

1.2-1.5 = 1.3 10/4.47213 =2.236 1.3/2.236= -0.134
p value= .3669?

but i get .4483

There must be more to the question than just this! And what have I said about the setting out ....!?

Is it the sample standard deviation or the population standard deviation?

If the latter, than the z-statistic is appropriate and the p-value is 0.4467 (correct to four decimal places).

If the former, than the t-statistic is appropriate (provided the data come from a normal population) and the p-value is 0.4474 (correct to four decimal places).