According to​ researchers, the mean length of imprisonment for​ motor-vehicle-theft offenders in a nation is 14.5 months. One hundred randomly selected​ motor-vehicle-theft offenders in a city in the nation had a mean length of imprisonment of 16.2 months.
At the 5​% significance​ level, do the data provide sufficient evidence to conclude that the mean length of imprisonment for​ motor-vehicle-theft offenders in the city differs from the national​ mean? Assume that the population standard deviation of the lengths of imprisonment for​ motor-vehicle-theft offenders in the city is 7.0 months.

Respuesta :

Answer:

[tex]z=\frac{16.2-14.5}{\frac{7}{\sqrt{100}}}=2.429[/tex]    

The p value for this case is given by:

[tex]p_v =2*P(z>2.429)=0.015[/tex]  

The p value for this case is lower than the significance level so then we can conclude that the true mean is significantly different from 14.5 months

Step-by-step explanation:

Information given

[tex]\bar X=16.2[/tex] represent the sample mean

[tex]\sigma=7[/tex] represent the population standard deviation

[tex]n=100[/tex] sample size  

[tex]\mu_o =14.5[/tex] represent the value that we want to check

[tex]\alpha=0.05[/tex] represent the significance level

z would represent the statistic

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

System of hypothesis

We want to check if the true mean is different from 14.5, the system of hypothesis would be:  

Null hypothesis:[tex]\mu = 14.5[/tex]  

Alternative hypothesis:[tex]\mu \neq 14.5[/tex]  

The statistic is given:

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

The statistic is given by:

[tex]z=\frac{16.2-14.5}{\frac{7}{\sqrt{100}}}=2.429[/tex]    

The p value for this case is given by:

[tex]p_v =2*P(z>2.429)=0.015[/tex]  

The p value for this case is lower than the significance level so then we can conclude that the true mean is significantly different from 14.5 months