Question

The Toylot company makes an electric train with a motor that it claims will draw an average of only 0.8 ampere (A) under a normal load. A sample of nine motors was tested, and it was found that the mean current was x = 1.32 A, with a sample standard deviation of s = 0.44 A.

Do the data indicate that the Toylot claim of 0.8 A is too low? (Use a 1% level of significance.)

Answer 1

The data indicate that toylot claim t(s) = - 3,54

Explanation:

T student distribution

sample size n = 9 df = n - 1 df = 9 - 1 df = 8

sample mean μ = 1.32

sample standard deviation σ = 0,44

1.- Test hypothesis

H₀ null hypothesis μ₀ = 0,8

Hₐ alternative hypothesis μ₀ < 0,8

2.- Critical value

Confidence interval 99 % α = 0,01 and df = 8

t(c) = - 2.8965

3.-Compute t(s)

t(s) = [ ( μ - μ₀ ) / s/√n ] t(s) = - 0,52 * 3/ 0,44 t(s) = - 3.54

4.- Compare t(s) and t(c)

t(s) is far away in the rejection region. The data indicate that toylot claim is too low