Question

The weights of a sample of college textbooks has a bell-shaped distribution with a mean of 8.1 p o u n d s ( l b s ) and a standard deviation of 2.1 l b s . According to the Empirical Rule, what percent of all college textbooks will weigh between 1.8 and 14.4 l b s ?

Answer 1

Answer:

The interval    ( 1,8 ; 14,4 ) will contains 99,7 % of all values      

Step-by-step explanation:

For Normal Distribution  N ( μ ; σ ) the Empirical Rule establishes that in the intervals:

( μ  ±  σ )   we find  68,3 % of all values

( μ  ±  2σ ) we find  95,4 % of all values

( μ  ±  3σ ) we find  99,7 % of all values

Then we have a normal distribution  N ( 8,1 ; 2,1 )

3*σ  =  3* 2,1 = 6,3

And   8,1 - 6,3  = 1,8             8,1  + 6,3  = 14,4

Then the interval    ( 1,8 ; 14,4 ) will contains 99,7 % of all values