at a school number of boys : number of girls =9:7. There are 116 more boys than girls. Work out the total number of students at
2 answers:
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If two events are independent, then
.
Use formulas for conditional probabilities:
.
For independent events these formulas will be:
.
Now in your case and
.
This shows that the only correct choice is A.
We reject our null hypothesis, H₀, at a level of significance of =0.01 since the P-value is less than that threshold. There is compelling statistical data to indicate that since 1991, the proportion of drivers who love driving has decreased.
Given,
The Pew Research Center recently polled n=1048 U.S. drivers and found that 69% enjoyed driving their automobiles.
In 1991, a Gallup poll reported this percentage to be 79%. using the data from this poll, test the claim that the percentage of drivers who enjoy driving their cars has declined since 1991.
To report the large-sample z statistic and its p-value,
Null hypothesis,
H₀ : p = 0.79
Alternative hypothesis,
Ha : p < 0.79
Level of significance, α = 0.01
Under H₀
Test statistic,
Z₀ = -7.948
The alternative hypothesis(Ha) is left-tailed, so the P-value of the test is given by
P-value = P(z <-7.945)
= 0.000 (from z-table)
Since the P-value is smaller than given level of significance, α=0.01 we reject our null hypothesis, H₀, at α=0.0.1 level Strong statistical evidence to conclude that the percentage of drivers who enjoy driving their cars has declined since 1991.
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