STATS 107: Exam 2 REVIEW
CHAPTER 12: Mean. The mean of the three numbers: 1, 2, and 15 is equal to...
mean > add all the numbers / by the amount of numbers 1 + 2 + 15 / 3 = 6
CHAPTER 12: Median. The median of the three numbers: 1, 2, and 15 is equal to...
median = the middle number 2
CHAPTER 13: The mean and median. Which of the following is an incorrect statement?
the median is the balance point in a density curve
CHAPTER 12: Standard deviation. Which of the following statements is true of the standard deviation?
removing an outlier will decrease the standard deviation
CHAPTER 11: Shape of distributions. In a certain town, most haircuts are between $10 and $20, but a few salons cater to high-end clients and charge $30 to $60. The distribution of haircut prices is...
skewed to the left
CHAPTER 11: Shape of distributions. The following figure exam scores for 75 students. What is the shape of the exam score distribution?
skewed to the left
CHAPTER 9: Academic good standing. To be in good standing at college, a student needs to maintain a certain grade point average (GPA). Typically, a student who falls below 2.0 is put on academic probation for at least a semester. At a local college, administrators wanted in increase the GPA to remain in good standing from a 2.0 and reported that the anticipated increase of students on probation would be from 3% to 5% of the student body. Relatively speaking, the increase in the percentage of students at the college who would be on a academic probation would be...
67% over the current figure
CHAPTER 9: Deer in the suburbs. Westchester County is a suburban area covering 438 square miles immediately north of New York City. A garden magazine claimed that the county is home to 800,000 deer. Do a calculation that shows this claim to be implausible. How does the number you calculated show that this claim is implausible?
800,000 deer / 438 square miles = 1,826 deer per square mile-- this number seems too high to be plausible
CHAPTER 13: More on pulse rates. Let's again assume that the resting pulse rates for healthy adults follow a Normal distribution with a mean of 69 beats per minute and a standard deviation of 9.5 beats per minute. When converted to a standard score, Adam's pulse rate becomes -0.5. How should this standard score be interpreted?
Adam's pulse rates is about one half of a standard deviation below the mean
CHAPTER 13: Reading test scores. A standardized reading test is given to fifth-grade students. Scores on this test are Normally distributed, with a mean of 32 points and a standard deviation of 8 points. When Corey gets his test results, he is told his score is at the 95th percentile. What does this mean?
Corey's score is higher than 95% of the students who took this test
CHAPTER 12: Here are data on the percentages of words of 1 to 15 letters used in articles in Popular Science magazine. Find the five-number summary of the distribution of word lengths from this table.
MIN= 0.2 Q1= 1.5 ? MEDIAN= 4.4 > if the amount of numbers is odd it's the middle number > if the amount of numbers is even it's the 2 middle numbers, added up then divided by 2 Q3= 10.35 ? MAX= 18.7
CHAPTER 15: Causation. The best evidence that changes in one variable cause changes in another comes from...
randomized comparative experiments
CHAPTER 9: Classes on Fridays. A professor is concerned that not enough courses at his college hold class meetings on Friday's. After speaking with administrators, the professor finds out that 15% of courses have class meetings on Friday's. At this school, classes meet on either Monday-Wednesday-Friday or Tuesday-Thursday and do not meet on Saturday or Sunday.
We cannot make a decision about the 15% figure because we do not know how courses are divided among teaching days (e.g., Monday-Wednesday-Friday or Tuesday-Thursday)
CHAPTER 12: The five-number summary. Which of the following is a graph of the five-number summary?
a boxplot
CHAPTER 11: Where do 18- to 44-year-olds live? Figure 11.11 is a stemplot of the percentage of residents aged 18 to 44 in each of the 50 states in 2010. As in Figure 11.6 (page 253) for older residents, the stems are whole percents and the leaves are tenths of a percent. a) It turns out that Utah has the largest percentage of residents aged 18 to 44 years. What is the percentage for this state? b) describe the shape, center, and variability of this distribution.
a) Utah has 39.7% young adults b) the distribution is roughly symmetric, centered at 35.85%, and spread from 32.5% to 39.7%
CHAPTER 15: The 2008 and 2012 presidential elections. Democrat Barack Obama was elected president in 2008 and 2012. The following figure plots the percentage who voted for Obama in 2008 and 2012 for each of the 50 states and the District of Columbia. a) Describe in words the direction, form, and strength of the relationship between the percentage of votes for Obama in 2008 and the percentage in 2012 b) The correlation between these variables is r=0.983. What percentage of the observed variation in 2012 percentages can be explained by straight-line dependence on 2008 percentages?
a) direction= positive form= linear strength= strong b) (0.983)^2 = 96.63%
CHAPTER 14: Correlation. Which of the following is true of the correlation r?
all of the above -it cannot be greater than 1 or less than -1 - it measures the strength of the straight-line relationship between two quantitative variables -a correlation of +1 or -1 can only happen if there is a perfect straight-line relationship between two quantitative variables
CHAPTER 9:Stocks go down. On February 5, 2018, the Dow Jones Industrial Average dropped 1,175 points from its opening level of 25,521. This was the biggest one-day point decline ever. By what percentage did the Dow drop that day?
amount of difference / original amount x 100% = percent difference 1,175 / 25,521 x 100% = 4.6%
CHAPTER 9: Stocks go down. On October 19, 1987, the Dow Jones Industrial Average dropped 508 points from its opening level of 2,245. By what percentage did the Dow drop that day? This was the biggest one-day percentage drop ever.
amount of difference / original amount x 100% = percent difference 508 / 2,245 = 22.63%
CHAPTER 13: Pulse rates. Suppose that resting pulse rates for healthy adults are found to follow a Normal distribution, with a mean of 69 beats per minute and a standard deviation of 9.5 beats per minutes. If Bonnie has a pulse rate of 78.5 beats per minute, this means that...
approximately 16% of adults have pulse rates higher than Bonnie's
CHAPTER 15: Prediction. An observed relationship between two variables can be used for prediction...
as long as the patterns found in past data continue to hold true
CHAPTER 15: Extrapolation. Extrapolation, or prediction outside the rand of the data, is risky...
because the pattern observed in the data may be different outside the range of the data
CHAPTER 10: Categorical and quantitative variables. A survey was conducted and respondents were asked what color car they drive and how many miles they travel per day. The variable type for "car color" and "miles per day" are...
car color is categorical, miles per day is quantitative
CHAPTER 13: Density curves. One characteristic of a density curve is that there is a specific total area under the curve. What is this area equal to?
exactly 1
CHAPTER 14: Creating scatterplots. When creating a scatterplot,
if you have an explanatory variable, put it on the horizontal axis
CHAPTER 15: Least-squares. The least-squares regression line...
is the line that makes the sum of the squared vertical distances of the data points from the line as small as possible
CHAPTER 10: Which graph? You cant to show how the price of cable television has changed over the years. You should use a...
line graph
CHAPTER 14: Interpreting scatterplots. If the points in a scatterplot of two variables slope downward from left to right, we say the direction of the relationship between the variables is...
negative
CHAPTER 9: Decreasing household trash. A large city started a new recycling program that aims to reduce household trash by 25% by educating residents about more household items that can be recycled. A friend of yours says, "This is great! The amount of recycling will increase by 25%. That's a great start!" What is wrong with your friend's comment?
none of the above
CHAPTER 11: Stemplots. An advantage of a stemplot over a histogram is...
one can recover the actual observations from the display
CHAPTER 15: Correlation. The quantity that tells us what fraction of the variation in the responses is explained by the straight-line tie between the response and explanatory variables is...
the square of the correlation
CHAPTER 10: Distributions. A recent report on the religious affiliation of Hispanics says 55% are Catholic, 22% Protestant, 18% unaffiliated, and 4% other. This adds up to 99%. You conclude...
this is due to roundoff error
CHAPTER 11: Histograms. Use a histogram when...
you want to look at the distribution of a quantitative variable