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In 2010, the average finishing time for marathons across the US was approximately 278 minutes, with a standard deviation of approximately 63 minutes. What finishing time defines the fastest 7.93% of runners?

Respuesta :

Chimara

Answer:

336 minutes

Step-by-step explanation:

Mean finishing time: 278 minutes

Standard Deviation: 63 minutes

Confidence interval: [278 - 63] , [278 + 63]  = [215 , 341] minutes

What finishing time defines the fastest 7.93% of runners?

This means the 7.93% of time closest to the upper limit of 341 minutes

341 - 215  ≡  63 × 2  = 126

7.93% of 126  = 0.0793 × 126  = 9.9918

341 - 9.9918 = 331.0082

Hence the finishing time that defines the fastest 7.93% of runners has an interval of [331 , 341] minutes with a mean or average of 336.0041 ≅ 336 minutes

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