HP 39gs Master Manual page 144

Hypothesis test: T-Test
A farmer compared the 15-day mean weight of two sets of chicks, one group receiving feed
supplement A and the other supplement C. Twenty two chicks only one day old were assigned
randomly to the two groups. To distinguish between the two groups of eleven, which were caged
together to minimize other influences, the heads of the chicks were stained red and purple
respectively with a harmless vegetable dye.
The individual weights were recorded in the table below. From the means at the end of the table it
appears that supplement A produces a higher mean weight.
Supp. A 57 120
Supp. C 89 30
The farmer wishes to know, at the 1% test level, whether this is statistically significant.
Our hypotheses are:
H : The effects are the same
0
H : Supplement A is better
A
Enter the data into columns
Since we know the standard deviations of only these samples, we must
again use a Student-t test.
import the summary statistics. The import screen can be seen on the
right.
The results of the importation can be seen right. Since the two standard
deviations for the samples are similar, and the sample sizes are the
same, a more accurate estimate of the population standard deviation will
be obtained if the data is pooled, so ensure that this option is
µ µ
-
1 2
Weights
101 137 119 117
82 50 39
( )
µ µ
=
1 2
( )
µ µ
>
1 2
and of the Statistics aplet.
C1 C2
We are dealing with two independent samples in this case and so we
need to choose from those tests which involve two samples.
We then change to the
104 73 53
22 57 32 96
ie. There is no effect from the supplement.
view to
NUM SETUP
ed.
144
x
68 118 97
31 88 56
σ
X
27.75
26.54