Question

1-A certain group of test subjects had pulse rates with a mean of 75 beats per minute and a standard deviation of 17.7 beats per minute. A pulse rate of what would be significantly low?

2-The blood platelet counts of a group of women have a bell-shaped distribution with a mean of 346.4 and a standard deviation of 23.7. What is the approximate percentage of women with platelet counts within three standard deviations of the mean?

Answer 1

Solution :

1) Given that,

mean = = 75

standard deviation = = 17.7

significantly low = - 2

significantly low = 75 - 2 * 17.7

significantly low = 39.6 beats per minute.

2) Given that,

mean = = 346.4

standard deviation = = 23.7

Using Empirical rule,

P( - 3 < x <   + 3 ) = 99.7%

= P( 346.4 - 3 * 23.7 < x < 346.4 + 3 * 23.7 ) = 99.7%

= P( 346.4 - 71.1 < x < 346.4 + 71.1 ) = 99.7%

=P( 275.3 < x < 417.5 ) = 99.7%