Question

. A soccer ball manufacturer claims the diameters of their ball have a standard deviation of 2 mm when properly inflated. Based on a random sample of 10 balls you find a standard deviation of 3.2 mm. Does the sample suggest the standard deviation is higher than that claimed by the manufacturer?

Answer 1

Yes, there is significant evidence to support the claim that sample standard deviation is higher than that claimed by the manufacturer

Explanation:

Sample standard deviation, s = 3.2

Population standard deviation, σ = 2

Defining the Null and alternative hypothesis :

H0 : σ = 2

H1 : σ > 2

The test statistic :

Use the Relation :.

[(n - 1)*s²] ÷ σ²

[(10 - 1) * 3.2²] ÷ 2²

(9 * 10.24) ÷ 4

92.16 ÷ 4

= 23.04

We obtain the Pvalue for the distribution :

Using the Pvalue from Chisquare distribution calculator :

Pvalue(Chisquare score, df)

df = n - 1 = 10 - 1 = 9

Pvalue(23.04, 9) = 0.006107

Decision :

If Pvalue is < α ; Reject H0 ; α = 0.05

0.006107 < 0.05 ; We reject H0