A manufacturer of watches has established that on the average his watches do not gain or lose. He also would like to claim that at least 95% of the watches are accurate to ±0.2 s per week. A random sample of 15 watches provided the following gains (+) or losses (-) in seconds in 1 week:

Can the claim be made with a 5% chance of being wrong? (Assume that the inaccuracies of these watches are normally distributed.)

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+0.17 +0.01 +0.08 - -0.07 + 0.06 +0.11 +0.13 +0.08 +0.05 -0.05 +0.23 - -0.14 -0.10 -0.87 + 0.05