Answer: 37
Step-by-step explanation:
Given : Significance level :
Critical value :
margin of error : E= 1 mile per gallon
Population standard deviation: miles per gallon.
We know that when the population standard deviation is known then the formula to find the sample size is given by :
[Round to the next whole number.]
Hence, the required number of automobiles should be used in the test = 37
Answer:
The reason why standard deviation of the entire class is greater than standard deviation of males and females considered separately, is that mean values for males and females are different from each other.
Step-by-step explanation:
The concept of mean is well represented by the following formula
mean = , where x1, x2, xn are the observations and N is the number of observations (population).
Standard deviation represents the distance between each observation and the mean of the population (all observations). The formula for this parameter is:
Standard deviation =√[((x1 - x)² + (x2-x)² + ....+ (xn-x)²)/N-1], where x1, x2,..., xn are the observations and x is the mean value.
In this case you have that each height registered is an observation and the number of observations represents the N value. As you can see if the mean for males is different from that of females their standard deviation will be different too. Usually males have heigths greater than that of females (1.77 vs 1.64, in USA for example), and heights inside each group will be more similar than between groups. Then, when you mix all observation there will be an increase in standard deviation, because you are mixing very different heigths
Answer:
Step-by-step explanation:
Given
x² - 3x
To make the expression a perfect square
add ( half the coefficient of the x- term )²
x² + 2( - )x +
, thus
x² - 3x +
= (x - )² ← a perfect square