Answer:
d. t-test for means
Step-by-step explanation:
Options are "a. z-test for proportions, b. z-test for means, c. none of the other three answers, d. t-test for means"
Sample size = n = 120
Sample mean = x = 0.8
Sample standard deviation = s = 2
Claim: A particular diet helps loss weight.
Hypothesis test
The null and alternative hypothesis is
H0 : μ = 0
Ha : μ < 0
Now, when population standard deviation is unknown we use t-test otherwise use z-test. So, the kind of hypothesis testing that we use is t-test for means.