A study found that, in 2005, 12.5% of U.S. workers belonged to unions ( The Wall
ID: 3124508 • Letter: A
Question
A study found that, in 2005, 12.5% of U.S. workers belonged to unions (The Wall Street Journal, January 21, 2006). Suppose a sample of 400 U.S. workers is collected in 2006 to determine whether union efforts to organize have increased union membership.
Formulate the hypotheses that can be used to determine whether union membership increased in 2006.
H0: p
Ha: p
If the sample results show that 52 of the workers belonged to unions, what is the sample proportion of workers belonging to unions (to 2 decimals)?
Complete the following, assuming an level of .05.
Compute the value of the test statistic (to 2 decimals).
What is the p-value (to 4 decimals)?
What is your conclusion?
Explanation / Answer
A)
Formulating the null and alternatuve hypotheses,
Ho: p <= 0.125
Ha: p > 0.125 [ANSWER]
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B)
Getting the point estimate of p, p^,
p^ = x / n = 0.13 [ANSWER, SAMPLE PROPORTION]
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C)
As we see, the hypothesized po = 0.125
Getting the standard error of p^, sp,
sp = sqrt[po (1 - po)/n] = 0.016535946
Getting the z statistic,
z = (p^ - po)/sp = 0.30 [ANSWER, TEST STATISTIC]
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D)
As this is a 1 tailed test, then, getting the p value,
p = 0.3821 [ANSWER, P VALUE]
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e)
As P > 0.05, then we fail to reject Ho.
There is no significant evidence that union membership increased in 2006 at 0.05 level. [CONCLUSION]
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