Question

I'm trying to solve this... (for stats)

Erika, Amber and Edwin co-creators of KrakBerry Spa Shoppe claim that their Acai Facial Blend will keep a woman’s’ skin supple and healthy looking for at least 65 days. Esthela, a consumer advocate, tested 15 bottles of the Acai Facial Blend and found a mean of 63 days with a standard deviation of 2 days. Test at the 10% significance level whether the company’s claim is true.

Answer 1

Solution-:

Given:

Here, is unknown so we use t-test

(1)To test,

Vs (Left tailed /one tailed)

(2) The test statistic is given by,

(3) Critical value or Table value:-

(form t-table)

Or (by using MS-Excel command"=TINV(0.2,14)")

(4) Decision Rule:- We reject if   and accept otherwise .

Here, hence   
        we reject (i.e fail to accept )  at 10% l.o.s.

(5) Conclusion:- We conclude that , their Acai Facial Blend will keep a woman’s’ skin supple and healthy looking not  at least 65 days. (i.e. less than 65 days)

Hence, we say that the company claim is not true.