A cement manufacturer claims that concrete prepared from its product has a relatively stable compressive strength and that the strength measured in kilograms per square centimetre (kg/cm) lies within a range of 40 kg/cm. A sample of n = 10 measure- ments produced a mean and variance equal to, respectively,

Do these data present sufficient evidence to reject the manufacturer's claim?

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x=312 312 and $2 s = 195