A safety officer wants to prove that μ = the average speed of cars driven by a school is less than 25 mph. Suppose that a random sample of 14 cars shows an average speed of 24.0 mph, with a sample standard deviation of 2.2 mph. Assume that the speeds of cars are normally distributed. What is the p-value?

Respuesta :

Answer:

[tex]t=\frac{24-25}{\frac{2.2}{\sqrt{14}}}=-1.70[/tex]    

The degrees of freedom are given by:

[tex]df=n-1=14-1=13[/tex]  

The p value for this case would be given by:

[tex]p_v =P(t_{(13)}<-1.70)=0.0565[/tex]  

Step-by-step explanation:

Information given

[tex]\bar X=24[/tex] represent the mean height for the sample  

[tex]s=2.2[/tex] represent the sample standard deviation

[tex]n=14[/tex] sample size  

[tex]\mu_o =25[/tex] represent the value that we want to test

t would represent the statistic

[tex]p_v[/tex] represent the p value for the test

Hypothesis to verify

We want to cehck if the true mean is lees than 25 mph, the system of hypothesis would be:  

Null hypothesis:[tex]\mu \geq 25[/tex]  

Alternative hypothesis:[tex]\mu < 25[/tex]  

The statistic would be given by:

[tex]t=\frac{\bar X-\mu_o}{\frac{s}{\sqrt{n}}}[/tex]  (1)  

Replacing the info given we got:

[tex]t=\frac{24-25}{\frac{2.2}{\sqrt{14}}}=-1.70[/tex]    

The degrees of freedom are given by:

[tex]df=n-1=14-1=13[/tex]  

The p value for this case would be given by:

[tex]p_v =P(t_{(13)}<-1.70)=0.0565[/tex]