Question

Baby weights: According to the 2010 National Health Statistics Reports, the weight of male babies less than 2 months old in the United States is normally distributed with mean 11.5 pounds and standard deviation 2.7 pounds.

a. What proportion of babies weigh more than 13 pounds?

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b. What proportion of babies weigh less than 15 pounds?

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c. What proportion of babies weigh between 10 and 14 pounds?

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d. Is it unusual for a baby to weigh more than 17 pounds?

Answer 1

Given that the weight of male babies of less than 2 months in United States are normally distributed with mean pounds and standard deviationpounds.

a.

To compute the proportion of the population that is more than 13 pounds using Minitab follow the steps given below.

1. Click Calc, then select Probability distributions and then go to Normal.

2. Select the Cumulative option.

3. Enter 11.5 in the Mean field and enter 2.7 in the standard deviation field.

4. Enter 13 in the input constant field.

5. Click Ok. The final output is given below.

The required proportion is,

The required answer is

b.

Similarly, compute the probability that a randomly chosen value is less than 15 pounds using Minitab. The final screenshot is given below.

The required probability is,

The required answer is

c.

To compute the proportion of the population that is between 10 and 14 using Minitab follow the steps given below.

1. Click Calc, then select Probability distributions and then go to Normal.

2. Select the Cumulative option.

3. Enter 11.5 in the Mean field and enter 2.7 in the standard deviation field.

4. Enter 10 in the input constant field.

5. Click Ok. The final output is given below.

Similarly, compute the probability when x is 14. The final output is given below.

The required proportion of the population that is between 10 and 14 is,

The required answer is

d.

Find the probability that a randomly chosen value is less than 17 pounds using Minitab. The final output is given below.

The required probability is

The probability is very high. Hence, it can be said that it is unusual for a baby to weigh more than 17 pounds.