A psychologist claims that the mean age at which children start walking is 17 months. latif wanted to check if this claim is true. He took a random sample of 20 children and found that the mean age at...

A psychologist claims that the mean age at which children start walking is 17 months. latif wanted to check if this claim is true. He took a random sample of 20 children and found that the mean age at which these children started walking was 15 months. It is known that the ages at which all children start walking are approximately normally distributed with a standard deviation of 3 months. By using the p-value approach, test that the mean age at which all children start walking is less than 17 months at 5% level of significance with mentioning all six steps.

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