In many animal societies, a role assumed by the adult male is a sentry, warning
ID: 3361574 • Letter: I
Question
In many animal societies, a role assumed by the adult male is a sentry, warning adult females and juveniles of approaching predators. Some students of animal behavior believe that this occurs in human society also. In one 4-month study in Seattle an investigator observed people crossing the street at an intersection with no traffic control. The observed behavior was the scanning behavior ("looking both ways") of adult males and females. The investigator reasoned that if the adult male assumed a protective sentry role, the scanning rate when alone would be less than when accompanied by an adult female. Data from this study is given below. Conduct hypothesis test using a=.05. USE MINI tab!
Male Scanning ("Looking both ways") Behavior
Situation Scanned Did Not Totals
Scan
Alone
56
28
84
With adult female
61
15
76
Male Scanning ("Looking both ways") Behavior
Situation Scanned Did Not Totals
Scan
Alone
56
28
84
With adult female
61
15
76
Explanation / Answer
Result:
n many animal societies, a role assumed by the adult male is a sentry, warning adult females and juveniles of approaching predators. Some students of animal behavior believe that this occurs in human society also. In one 4-month study in Seattle an investigator observed people crossing the street at an intersection with no traffic control. The observed behavior was the scanning behavior ("looking both ways") of adult males and females. The investigator reasoned that if the adult male assumed a protective sentry role, the scanning rate when alone would be less than when accompanied by an adult female. Data from this study is given below. Conduct hypothesis test using a=.05. USE MINI tab!
Test and CI for Two Proportions
Method
p: proportion where Sample 1 = Event
p: proportion where Sample 2 = Event
Difference: p - p
Descriptive Statistics
Sample
N
Event
Sample p
Sample 1
84
56
0.666667
Sample 2
76
61
0.802632
Estimation for Difference
Difference
95% Upper
Bound for
Difference
-0.135965
-0.022841
CI based on normal approximation
Test
Null hypothesis
H: p - p = 0
Alternative hypothesis
H: p - p < 0
Method
Z-Value
P-Value
Normal approximation
-1.94
0.026
Fisher's exact
0.039
The pooled estimate of the proportion (0.73125) is used for the tests.
This is lower tail test.
Calculated Z= -1.94, p=0.026 which is < 0.05 level.
Ho is rejected.
We conclude that the scanning rate when alone is less than when accompanied by an adult female.
p: proportion where Sample 1 = Event
p: proportion where Sample 2 = Event
Difference: p - p
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