The blood platelet counts of a group of women have a bell-shaped distribution with a mean of 258.7 and a standard deviation of 63.5. (All units are 1000 cells/muL.) 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 68.2 and 449.2? b. What is the approximate percentage of women with platelet counts between 195.2 and 322.2?

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dfbustos dfbustos · Answer 1 · 2020-06-11T05:24:26+02:00

Answer:

a) [tex]P( \mu -3\sigma <X< \mu +3\sigma)[/tex]

And from the empirical rule we know that this probability is 0.997 or 99.7%

b)[tex] P(195.2 <X<322.2)[/tex]

Using the z score we have:

[tex] z = \frac{322.2 -258.7}{63.5}= 1[/tex]

[tex] z = \frac{195.2 -258.7}{63.5}= -1[/tex]

And within one deviation from the mean we have 68% of the values

Step-by-step explanation:

For this case we defien the random variable of interest X as "blood platelet counts" and we know the following parameters:

[tex] \mu = 258.7, \sigma =63.5[/tex]

Part a

We can use the z score formula given by:

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

And we want this probability:

[tex]P( \mu -3\sigma <X< \mu +3\sigma)[/tex]

And from the empirical rule we know that this probability is 0.997 or 99.7%

Part b

For this case we want this probability:

[tex] P(195.2 <X<322.2)[/tex]

Using the z score we have:

[tex] z = \frac{322.2 -258.7}{63.5}= 1[/tex]

[tex] z = \frac{195.2 -258.7}{63.5}= -1[/tex]

And within one deviation from the mean we have 68% of the values