Answer:
a
The null hypothesis is
The Alternative hypothesis is
b
c
d
Yes the mean population is significantly less than 21.
Step-by-step explanation:
From the question we are given
a set of data
20 18 17 22 18
The confidence level is 90%
The sample size is n = 5
Generally the mean of the sample is mathematically evaluated as
The standard deviation is evaluated as
Now the confidence level is given as 90 % hence the level of significance can be evaluated as
%
Now the null hypothesis is
the Alternative hypothesis is
The standard error of mean is mathematically evaluated as
substituting values
The test statistic is evaluated as
substituting values
The critical value of the level of significance is obtained from the critical value table for z values as
Looking at the obtained value we see that is greater than the test statistics value so the null hypothesis is rejected