# Question: Eighty randomly selected batteries were tested to determine their lifetimes

Eighty randomly selected batteries were tested to determine their lifetimes (in hours). The following frequency distribution was obtained.

Class boundaries Frequency

62.5–73.5..........5

73.5–84.5 .........14

84.5–95.5 .........18

95.5–106.5.........25

106.5–117.5..........12

117.5–128.5.........6

Can it be concluded that the lifetimes of these brands of batteries are consistent?

Find the variance and standard deviation.

Class boundaries Frequency

62.5–73.5..........5

73.5–84.5 .........14

84.5–95.5 .........18

95.5–106.5.........25

106.5–117.5..........12

117.5–128.5.........6

Can it be concluded that the lifetimes of these brands of batteries are consistent?

Find the variance and standard deviation.

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