IDS 270 EXAM 1 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026

IDS 270 EXAM 1 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2026 What is the formula for finding residuals? - Answers y-yhat=residual When do you know a residual graph is over predicting? - Answers When the point on the residual graph is below the x-axis, meaning that it's negative. When do you know a residual graph is under predicting? - Answers When the point on the residual graph is above the x-axis, meaning it is a positive number How do you know a relationship between x & y is positive? - Answers If the slope is positive, the graph is positive, so that means it's a positive relationship between x & y How can you characterize the strength of the relationship between x & y? - Answers By calculating (r)^2. The closer r^2 is to 1, the stronger the relationship is. If x increases by 1, what is the predication for the change in y? - Answers The change in y is dependent on the amount of regression. If you: roll even on a red die, and roll an odd on a green die, these are __________ - Answers independent If you: roll an even on red and roll an odd on red, these are ____ - Answers disjoint Formula for the union of two probabilities? - Answers Pr(A U B)= P(a) + P(b) - Pr(A and B) Formula for: Pr(A and B)? - Answers P(a) * P(b) How do you know if two parts to a probability problem are independent of each other? - Answers If Pr(A and B) = P(a) * P(b) = Pr(A and B) Population Distribution - Answers Entire Population being used Sample distribution - Answers Initial samples taken from population distribution Sampling distribution - Answers Averages from all samples taken What shape is related to Central Limit Theorem? - Answers Bell shape Finding the Standard Deviation based on C.L.T - Answers S.D of population / Root( # in each sample If you compare two spreads, which number will be a tighter spread, big or small number? - Answers Smaller number What method do you use in order to get: What % of test takers can expect 700 or less - Answers X -- Z -- % Ex. General intelligence test has mean of 600, standard deviation of 60. what is percentile score for an exam of 700 (what percent of test takers get 700 or less) (x 700), x is 700, z= (700-600)/60= 1.66 Pr(z1.66) z= 1.6 on table a left to right- on top is for hundreths place. which is .06 What method do you use in order to get: What score is necessary to reach 90th percentile - Answers % -- Z -- X ex. general intelligence test mean of 600 and a standard deviation of 60. what score is necessary to reach 90th percentile? .9 in BODY of table A is 1.28( the value is .8997 closest to .9) so solve 1.28=(x-600/60) leads to 676.8 In order to figure out what score is necessary to reach a certain percentile? What do you need to use to convert to % to the number needed for the equation? - Answers Table A When talking about X -- Z -- % and vice versa; Format for (___ , ___) is - Answers (mean, standard deviation) Formula to compute X -- Z -- % and vice versa - Answers (score-mean)/(Standard Deviation) When is Simpson's Paradox proven? - Answers When the details disprove the conclusions drawn from the face-value data What is a sample? - Answers Amount of people tested. ex sample 40 voters from the population of ameri ca What is a statistic? - Answers a number calculated from a sample . Average score of testees. What is a parameter? - Answers a number that exists in a population. Ex. average height of all women in america What is a skyscraper? - Answers All data in one category What is a pancake? - Answers Too many categories = not a lot of data What does it mean to minimize chart ink? - Answers Cleaning up the chart What are some techniques to cleaning up chart ink? - Answers Taking away things like: Redundant legends, unnecessary lines and borders, etc. Define Non-Response bias - Answers Someone is selected for a sample and they do not respond. Define convenience sample - Answers Sampling those who are convenient to reach. ex mall intercepts, or asking the people on the floor of your dorm to fill out a survey Define response bias - Answers Not answering truthfully to sensitive questions/topics. Ex how much pot do you smoke (T/F) Bigger standard deviation, bigger spread - Answers True Define voluntary response sample - Answers Voluntarily giving data to a study. Ex people text to a phone number of they agree with a statement and text to a different one of they disagree Why could there be a difference between two departments? (3) - Answers Outliers, right-skewed charts, lurking variables When and only when can you compare the means of two charts? - Answers If they are symmetric Define Simpson's Paradox - Answers When aggregate data shows one result, but when you look at the details, you find a different result When finding a regression line, what is the formula for finding the slope? what is the formula for finding the y intercept? - Answers slope = (sy/sx) * r then y intercept = ybar-slope * xbar yhat= yintercept +slope What is the regression equation actually equal to? - Answers yhat If the x variable is increased by 1, what happens to y? - Answers The variable changes by the amount of the slope Variance formula - Answers r^2 How can you describe the strength of a regression relationship? - Answers The amount of variance. The closer to 100%, the better the relationship Define Bias - Answers Bias occurs when the center of the sampling distribution is not the same as the center of the population distribution How do you combat bias? - Answers Simple random sampling How do you combat variability? - Answers Larger sample For one variable at a time, what types of graphs/tables are categorical? (3) - Answers Bar chart, Pareto Chart, Pie Chart For one variable at a time, what types of numbers/computations are categorical? - Answers None For one variable at a time, what types of graphs/tables are quantitative? (3) - Answers Histogram, Box plot, Stem & Leaf plot For one variable at a time, what types of numbers/computations are quantitative? (2) - Answers Measure of center, measures of spread For two variables at a time, what types of graphs/tables are categorical? What chapter does this relate to? - Answers Two way table and their graphs? Chapter 2 For two variables at a time, what type of graph/table is quantitative? - Answers Scatterplot For two variables at a time, what type of numbers/computations are categorical? - Answers %'s from two-way charts For two variables at a time, what type of numbers/computations are quantitative? - Answers Correlations, regression slope Conditional Probability formula - Answers P(B|A)= P(A and B) / P(A) Disjoint definition - Answers Two events that are mutually exclusive that cannot occur at the same time. What a synonym for disjoint? - Answers Mutually exclusive Independent probability definition - Answers Two events are not mutually exclusive and can occur at the same time Define: observational study - Answers Observing behavior or ask people questions as they are going about their day to day lives. Ex: Call people and ask them how often they eat out Define: experiment - Answers Imposing some treatment on people and then observe their behavior or ask questions Ex. Give people a drug and then do chemical analysis of their blood