# Stat

## Stat

1. We ask if the attitudes toward fuel costs of 100 owners of hybrid electric cars (X = 76) are different from those on a national survey of owners of non-hybrid cars (μ = 65, σX = 24). Higher scores indicate a more positive attitude.
(a) Is this a one-or two-tailed test?
→ This is a two tailed test.
(b) In words, what are H0 and Ha ?
→ H0: Attitude towards fuel cost of hybrid owners is same as that of now-hybrid owners
Ha : they are different
(c) Perform the z-test.
→z-score = (76-65) /(24/sqrt(100))
= 11/2.4
= 4.5833
z-critical (assuming α = 0.05) = 1.96
(d) What do you conclude about attitudes here?
→ Since z-score is more than z-critical, attitude of hybrid owners towards fuel cost is different from that of non-hybrid owners.
(e) Report your results in the correct format.
→ Null hypothesis that attitude of hybrid owners is same as that of non hybrid owners is rejected at a level of significance α = 0.05.
2. You investigate whether the older or younger male in pairs of brothers tends to be more extroverted. You obtain the following extroversion scores:
Sample 1 (Younger)
Sample 2 (Older)
10
18
11
17
18
19
12
16
15
15
13
19
19
13
15
20
(a) What are H0 and Ha? (b) Compute tobt. (c) With ? 5 .05, what is tcrit? (d) What should you conclude about this relationship? (e) Which of our approaches should we use to determine if this a scientifically important relationship?
Since they are in pairs, it would be better to do a paired t-test.
Sample 1 (Younger)
Sample 2 (Older)
Diff
10
18
8
11
17
6
18
19
1
12
16
4
15
15
0
13
19
6
19
13
-6
15
20
5
a)
Ho: There is no difference between extroversion of older or younger males in brothers.
Ha: They are different
b) Sample Size n = 8
x̅ = 3, Standard Deviation s = 4.5040
tobt = 3/(4.5040/√8) = 1.883943
c)
tcrit (for α = 0.05 ( two tailed) and df=7) = 2.364624
d) Since tobt < tcrit null hypothesis cannot be rejected. Extroversion of elder or...