Question

The distribution of bladder volume in men is approximately Normal with mean 550 ml and standard deviation 100 ml.

Answer 1

Answer:

a) 15.866%

b) Middle 95% = 350 ml to 750 ml

c) 0.3829

d) Middle 90% of men’s bladder fall = 385.5ml to 714.5 ml

Step-by-step explanation:

We solve using z score formula

z-score is is z = (x-μ)/σ, where x is the raw score, μ is the population mean, and σ is the population standard deviation.

The distribution of bladder volume in men is approximately Normal with mean 550 ml and standard deviation 100 ml.

Required:

a. What percent of men have a bladder volume smaller than 450 ml?

z = 450 - 550/100

= -1

P-value from Z-Table:

P(x<450) = 0.15866

Convert to percentage

0.15866 × 100

= 15.866%

b. Between what volumes do the middle 95% of men’s bladders fall?

Middle 95% falls between 2 standard deviation of the mean

μ ± 2σ

μ - 2σ

550 - 2(100)

= 550 - 200

= 350 ml

μ + 2σ

= 550 + 2(100)

= 550 + 200

= 750 ml

Middle 95% = 350 ml to 750 ml

c. What proportion of male bladders are between 500 and 600 ml?

For 500ml

z = 500 - 550/100

= -0.5

Probability value from Z-Table:

P(x = 500) = 0.30854

For 600ml

z = 600 - 550/100

= 0.5

Probabilty value from Z-Table:

P(x = 600) = 0.69146

Proportion of male bladders are between 500 and 600 ml

P(x = 600) - P(x = 500)

0.69146 - 0.30854

= 0.38292

≈ 0.3829

d. What volumes do the middle 90% of men’s bladder fall?

The z score for middle 90% + / – 1.645

Hence,

1.645 = x - 550/100

1.645 × 100 = x - 550

164.5 + 550 = x

x = 714.5 ml

-1.645 = x - 550/100

-1.645 × 100 = x - 550

- 164.5 + 550 = x

x = 385.5ml

Middle 90% of men’s bladder fall = 385.5ml to 714.5 ml