A pediatrician wishes to study how the average weight Y (in kilograms) of children changes during the first year of life. He plo
1 answer:
Answer:
Answer is option a ) 0.53
Step-by-step explanation:
slope =
Given that a pediatrician wishes to study how the average weight Y (in kilograms) of children changes during the first year of life. He plots these averages versus the age X (in months) and decides to fit a least-squares regression line to the data with X as the explanatory variable and Y as the response variable.
He finds the following quantities:
r = correlation between X and Y= 0.84
x = mean of the values of X = 5.69
y = mean of the values of Y = 6.26
S_x = standard deviation of the values of X = 3.23
s_y = standard deviation of the values of Y = 2.04
Using the formula for slope given above substitute to get
round off to 0.53
Answer is option a ) 0.53
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Answer:
And if we solve for a we got
So the value of height that separates the bottom 85% of data from the top 15% is 25.27.
Step-by-step explanation:
Previous concepts
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent the finishing time of a population, and for this case we know the distribution for X is given by:
Where and
Solution to the problem
For this part we want to find a value a, such that we satisfy this condition:
(a)
(b)
Both conditions are equivalent on this case. We can use the z score again in order to find the value a.
As we can see on the figure attached the z value that satisfy the condition with 0.85 of the area on the left and 0.15 of the area on the right it's z=1.04. On this case P(Z<1.04)=0.85 and P(z>1.04)=0.15
If we use condition (b) from previous we have this:
But we know which value of z satisfy the previous equation so then we can do this:
And if we solve for a we got
So the value of height that separates the bottom 85% of data from the top 15% is 25.27.