Answer:
z(s) is in the rejection region. We reject H₀. We dont have enought evidence to support that the cream has effect over the recovery time
Step-by-step explanation:
Sample information:
Size n = 100
mean x = 28,5
Population information
μ₀ = 30
Standard deviation σ = 8
Test Hypothesis
Null Hypothesis H₀ x = μ₀
Alternative Hypothesis Hₐ x < μ₀
We assume CI = 95 % then α = 5 % α = 0,05
As the alternative hypothesis suggest we should develop a one tail-test on the left ( we need to find out if the cream have any effect on the rash), effects on the rash could be measured as days of recovery
A z(c) for 0,05 from z-table is: z(c) = - 1,64
z(s) = ( x - μ₀ ) / σ/√n
z(s) = ( 28,5 - 30 ) / 8/√100
z(s) = - 1,5 * 10 / 8
z(s) = - 1,875
Comparing z(s) and z(c)
|z(s)| < |z(c)| 1,875 > 1,64
z(s) is in the rejection region. We reject H₀. We dont have enought evidence to support that the cream has effect over the recovery time
