In: Statistics and Probability
You recently started working as a nurse manager at a larger local urgent care facility. Because the center is so new (and a bit fancier than most) many patients come here expecting a bit of a wait before they can be seen. Out of curiosity, on a particularly busy day you write down how many minutes a random sample of patients has to wait before being seen by one of the medical staff. Using a significance level of 20%, test whether the average wait time is less than 15 minutes.
12 |
10 |
15 |
17 |
15 |
18 |
15 |
15 |
10 |
15 |
12 |
10 |
12 |
19 |
10 |
14 |
10 |
17 |
13 |
15 |
23 |
12 |
15 |
20 |
7 |
10 |
16 |
14 |
14 |
14 |
18 |
13 |
A) What is the name of the type of hypothesis test required here? Is this a left-tailed, right-tailed, or two-tailed test? B) State AND verify all assumptions required for this test. [HINT: this test has two assumptions.] C) State the null and alternate hypotheses for this test: (use correct symbols and format!) Null hypothesis/Alternate hypothesis D) Run the correct test in Excel or on the TI-84 calculator and provide the information below. For each statistic provide the correct symbol and numeric value (round answers to 3 decimal places).Degrees of Freedom. Test Statistic.Critical Value. p-value E) State your statistical decision for this test and justify it using the statistics above. F) Interpret your decision within the context of the problem: what is your conclusion?
A)
Hypothesis test for one mean - t test
left tail test
b)
assumptions: random independent samples are used
population from which samples are taken is normally distributed
c)
Ho : µ = 15
Ha : µ < 15
d)
sample std dev , s = √(Σ(X- x̅ )²/(n-1) )
= 3.4355
Sample Size , n = 32
Sample Mean, x̅ = ΣX/n =
14.0625
degree of freedom= DF=n-1=
31
Standard Error , SE = s/√n = 3.43546494 / √
32 = 0.6073
t-test statistic= (x̅ - µ )/SE = ( 14.063
- 15 ) / 0.607
= -1.544
critical t value, t* =
-0.8534 [Excel formula =t.inv(α/no. of
tails,df) ]
p-Value =
0.0664 [Excel formula =t.dist(t-stat,df) ]
e)
Decision: p-value<α, Reject null hypothesis
f)
Conclusion: There is enough evidence to conlcude that average wait time is less than 15 minutes at 20% level of significance