In planning a study on the number of days in the last 30 that high school students texted while driving sometime during the day, a researcher states the hypotheses as H 0 : ¯ x = 15 days H a : ¯ x > 15 days What’s wrong with this? Hypotheses are statements about statistics, not parameters. The research question should not be about the population mean μ but should be about the sample mean ¯ x ˉ . Hypotheses are statements about parameters, not statistics. The research question should not be about the sample mean ¯ x , but should be about the population mean, μ . The null and alternative hypotheses need to be switched. There is nothing wrong with this statement.

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Ответ:

smokey13

01.09.2022

Mathematics

$2\frac{8}{11}$ hours.

Step-by-step explanation:

Let t represent time taken in hours by both working together.

So part of work completed by working together in 1 hour would be $\frac{1}{t}$ .

We have been given that working alone, Ryan can dig a 10 ft by 10 ft hole in five hours. So part of work completed by Ryan in 1 hour would be $\frac{1}{5}$ .

We are also told that Castel can dig the same while in six hours. So part of work completed by Castel in 1 hour would be $\frac{1}{6}$ .

Since they will work together, so we can equate sum of work completed by both as:

$\frac{1}{t}=\frac{1}{6}+\frac{1}{5}$

$\frac{1}{t}\times 30t=\frac{1}{6}\times 30t+\frac{1}{5}\times 30t$

30=5t+6t

30=11t

11t=30

$\frac{11t}{11}=\frac{30}{11}$

$t=2\frac{8}{11}$

Therefore, it will take $2\frac{8}{11}$ hours to dig the pool working together.

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