Question

the posted speed limit on a certain residential road is 30mph. the residents believe that drivers are speeding on this road on average. they observe 20 randomly selected drivers on this road, and find the mean speed to be 31.8mph with a standard deviation of 4.2mph. is the resident's belief accrue?

X= µ = n= x-bar= σ=

Answer 1

xbar = 31.8 , mu = 30 , n = 20 , sigma = 4.2

Below are the null and alternative Hypothesis,
Null Hypothesis, H0: μ = 30
Alternative Hypothesis, Ha: μ > 30

Test statistic,
t = (xbar - mu)/(s/sqrt(n))
t = (31.8 - 30)/(4.2/sqrt(20))
t = 1.917

P-value Approach
P-value = 0.0352
As P-value < 0.05, reject the null hypothesis.