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The belief is that the mean number of hours per week of part-time work of high school seniors in a city is 10.5 hours. Data from a simple random sample of 23 high school seniors indicated that their mean number of part-time work was 11.5 with a standard deviation of 1.4. Test whether these data cast doubt on the current belief. (use α = 0.05)

Required:
a. State your null and alternative hypotheses.
b. Sketch the rejection region.
c. Calculate the test statistic. Plot this value in your sketch in part b.
d. Determine the P-value for your test.
e. State your conclusions clearly in complete sentences.

Answer :

Answer:

a) See step by step explanation

b) See annex

c) t(s) = 3,4255

d) p- value  = 0,00146   or   0,15 %

e) See step by step explanation

Step-by-step explanation:

As n < 30 we use a t-student distribution

Population mean  μ₀ = 10,5

Sample size   n = 23

Degree of freedom      n - 1   =  22

Sample mean    μ  =  11,5

Sample standard deviation   s = 1,4

Confidence Interval  95 %

a) Null Hypothesis                     H₀             μ  =   μ₀

   Alternative Hypothesis         Hₐ              μ  >  μ₀

As CI  = 95 %      α = 5%    or   α = 0,05

We are solving a one tail-test  

With  df  =  22   and     α  = 0,05 in t-table we find t(c) = 1,7171

c)  t(s)  =  (   μ  -  μ₀ ) / s / √n

    t(s)  = ( 11,5 - 10,5 ) / 1,4 / √23

    t(s)  =   1 * 4,7958 / 1,4

    t(s)  =  3,4255

We compare t(s)  and t(c)

t(s) > t(c)   and t(s) is in the rejection region

Then we reject the null hypothesis.

d) P-value for    t(s) = 3,4255  is from t-table   equal to:

We find        for  df = 22    α = 0,001    and   α = 0,005

values of t                            

t                  3,505              2, 819           Δt   =  0,686

α                  0,001               0,005           Δα  =  0,004

with these values we interpolate by rule of three

0,686                          ⇒   0,004

(3,505 - 3,4255)       ⇒       x

x = 0,000463

and  P-value  =  0,00146    or  0,15 %

e) The p-value indicates  we are far away to consider the accptance of H₀

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