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The blood platelet counts of a group of women have a​ bell-shaped distribution with a mean of 255.4 and a standard deviation of 63.9. ​(All units are 1000 ​cells/mu​L.) Using the empirical​ rule, find each approximate percentage below. a. What is the approximate percentage of women with platelet counts within 3 standard deviations of the​ mean, or between 63.7 and 447.1​? b. What is the approximate percentage of women with platelet counts between 191.5 and 319.3​?

Respuesta :

Answer:

a) From the empirical rule we know that within 3 deviations from the mean we have 99.7% of the data

b) [tex] P(191.5<X<319.5)[/tex]

We can find the number of deviations from the mean for the limits using the z score formula given by:

[tex]z=\frac{x-\mu}{\sigma}[/tex]

And replacing we got:

[tex] z=\frac{191.5-255.4}{63.9}= -1[/tex]

[tex] z=\frac{319.3-255.4}{63.9}= 1[/tex]

So we have values within 1 deviation from the mean and using the empirical rule we know that we have 68% of the values for this case

Step-by-step explanation:

For this case we have the following properties for the random variable of interest "blood platelet counts"

[tex]\mu = 255.4[/tex] represent the mean

[tex]\sigma = 63.9[/tex] represent the population deviation

Part a

From the empirical rule we know that within 3 deviations from the mean we have 99.7% of the data

Part b

We want this probability:

[tex] P(191.5<X<319.5)[/tex]

We can find the number of deviations from the mean for the limits using the z score formula given by:

[tex]z=\frac{x-\mu}{\sigma}[/tex]

And replacing we got:

[tex] z=\frac{191.5-255.4}{63.9}= -1[/tex]

[tex] z=\frac{319.3-255.4}{63.9}= 1[/tex]

So we have values within 1 deviation from the mean and using the empirical rule we know that we have 68% of the values for this case

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