Stats Exam 2
Late in basketball game, the team that is behind often fouls someone in an attempt to get the ball back. Usually the opposing player will get to shoot foul shots "one on One" meaning he gets a shot, and then a 2nd shot only if he makes the 1st one. suppose the opposing player has made 74% of his foul shots this season. Estimate the number of points he will score in a one and one situation, if each foul shot made is worth one point.
1.29
Least squares means that the square of the largest residual is as small as it could possibly be.
False. Least squares means that the sum of the squares of all the residuals is minimized.
choose the linear model that passes through the most data points on the scatterplot.
False. the line usually touches none of the points, Minimize the sum of the squared errors.
Noting a recent study predicting the increase in cell phones costs, a friend remarks that by the times he's a grandfather, no one will be able to afford a cell phone. Explain where his thinking went awry.
He is extrapolating into the future. It is impossible to know if a trend like this will continue so far into the future.
a larger firm is considering acquiring a small bookstore. an analyst for the firm, noting that there is a strong, positive relationship between the number of sales people working and the amount of sales, suggests that when they acquire the store they should hire more people because that will drive higher sales. Is his conclusion Justified?
His conclusion is NOT JUSTIFIED. Correlation DOES NOT DEMONSTRATE causation. When there is a strong correlation, it is NOT JUSTIFABLE to conclude that the predictor variable caused the change. The analyst's argument is that sales staff causes sales. HOWEVER, IT MAY BE THE REVERSE, THAT MORE PEOPLE WERE HIRED AS SALES INCREASED.
A team of calculus teachers is analyzing student scores of final exam compared to midterm scores. One teacher proposes that they already have everu teacher's class averages and they should just work with those averages. Explain why problematic.
Individual student scores will vary greatly. The class averages will have much LESS variablilty and may DISGUISE important trends
what does b1 value mean, in this context?
It means that, on average, an additional increase of b1 X $1000 in sales is associates with each additional sales person working.
What does this b0 value mean, in this context? does this value of b0 make sense?
It means that, on average, the minimum amount of sales made from 2 sales people working is b0 X $1000. It does not make sense, because it is unlikely that any sales would be made with zero sales people working.
should new parents (who tend to worry) be concerned if their newborn's length and weight don't fit this equation?
NO. this is a model fit to data. No particular baby should be expected to fit this model exactly.
There is a strong correlation between the temperature and the number of skinned knees on playgrounds. Does this tell us that warm weather causes children to trip?
No. In warm weather more children will go outside and play.
A CEO complains that the winners of his "rookie jr executive of the year" award often turn out to have less impressive performance the following year. HE wonders whether the award actually encourages them to slack off. Can you off a better explanation?
Perhaps they weren't really better than other rookie executives, but just happened to have a lucky year.
Playing a board game, you are stuck in jail until you roll "doubles" (same numbers) on a pair of dice. YOu will simulate using random digits to estimate how many turns you expects to remain in jail. Identify the component if you were to run a simulation.
Rolling the pair of dice is the component
Admin's at university were interested in estimating the percentage of students who might attend a spring concert. The universities student body has about 44,000 members. How might the admin's answer their question by applying the 3 big ideas?
The admin's should take a survey. They should sample a part of the student body, selecting respondents with a randomization method. they should be sure to draw a sufficiently large sample.
A stat.s student properly simulated the length of checkout lines in grocery store and then reported, "the average length of the line will be 3.2 people." What is wrong with this conclusion?
The conclusion should indicate that the simulation suggests that the average length of the line would be 3.2 people. Future results might not match the simulated results exactly.
Use a random integer from 0 - 9 to represent the number of heads when 9 coins are tossed.
The outcomes are NOT equally likely. for ex, tossing 5 heads does not have the same likelihood as tossing 0-9 heads, but the simulation assumes they are equally likely.
a prof teaching a large lecture class of 350 students samples her class by rolling die. Then, starting with the row # on the die (1-6), she passes out a survey to every second row of the large lecture hall. she says this is a Simple Random Sample because everyone had an equal opportunity to sit in any seat and because she randomized the choice of rows. What do you think?
This is NOT an SRS. although each student may have an equal chance to be in the survey, groups of friends who choose to sit together will wither all be in or out of the sample, so the selection is not independent.
The residuals are observed y-values minus the y-values predicted by the linear model.
True. The residuals are the observed y-values minus the y-values predicted by the linear model.
An analyst tried fitting the regression line to each segment of data set separately to test a model of the whole data set and found the pot given below....
YES, each segment has a different best fit line so they follow DIFFERENT relationships.
Before R2 : 61.6 % After R2 :85.6% Does it appear that this outlier was exerting very much influence?
YES, this observation was influential. After it was removed, the slope of the regression line changed by a large amount.
Names are selected out of a hat to decide who washes the dishes. Is who washes dishes random?
Yes, who washes the dishes cannot be predicted before selecting the name.
If correlation is -.98 it indicates
a strong, negative association
select several dormitories at random and contact everyone living in the selected dorms.
cluster sample
Does correlation have units
no
Using a computer-based list of registered students, contact 100 freshman, 100 sophomores, 100jrs, and 100 srs, selected at random from each class.
stratified sample
using computer based alphabetical list of registered students, select one of the 1st 20 names on list at random, and then contact the student whose name is 40 names later, and then every 40th name after that.
systematic sample
what does given model mean?
the weight of newborn boy can be predicted as _____ Kg plus _____ kg per cm of length
Multiplying every value of x by 2
will not change the correlation