STAT 201; Exam 1 STUDY GUIDE VERIFIED CORRECT QUESTIONS AND ANSWERS LATEST UPDATED VERSION 2026/2027 (GRADED A+)

Relationship of Mean and Median in a Skewed Left Histogram? - Answer️Mean is less than median Is mean affected by outliers? - Answer️Sensitive to outliers, pulled in the direction of the skewness Is median affected by outliers? - Answer️NO! Measures of the Center - Answer️Mean, median,Mode Mean - Answer️center of gravity, is the balancing point for the observations Bar Graph - Answer️Used to measure qualitative data, to compare groups, and for many categories of the variable Which graph has the same shape as a bar graph but a different y axis? - Answer️Relative Frequency Chart Histograms vs. Bar Charts - Answer️Columns of histograms represents quantitative data and columns of bar charts represents a categorical data What is the most often observed data point? - Answer️Mode Variance - Answer️The average of the squared deviations of each observation from the mean Quartiles - Answer️Q1= 25th percentile Q2=50th percintile Q3=75th percentile Box Plot - Answer️This graph uses the numerical summaries of position to give a picture of the dataset When can we use the Empirical rule? - Answer️When we have symmetric and bell-shaped continuous data Z Score - Answer️the number of standard deviations an observation is from the mean Association - Answer️exists between two variables if particular values for one variable are more likely to occur with certain values of the other variable Contingency Table - Answer️is a display for two categorical variables. Its rows list the categories of one variable and its columns list categories of the other variable Scatterplot - Answer️used to examine the association or relationship between two quantitative variables Slope - Answer️is a measurement of how the line changes Regression line - Answer️predicts the response variable y as a straight-line function of the value x of the explanatory variable. Residual - Answer️The difference between a predicted value of y and an observed value of y for the same value of x is called a prediction error R2 - Answer️tells us the percentage of the response variable explained by the explanatory variable. Correlation Factor - Answer️gives us a sense of the strength of the linear relationship Slope - Answer️the change on average in the response variable for a unit increase in the explanatory variable Extrapolation - Answer️Using linear regression to make predictions for values of x that are outside of the range of collected data Why is extrapolation bad? - Answer️We did not estimate the relationship for values outside the range we observed. We have no guarantee that the relationship is still linear for our new value Influential Outliers - Answer️A single point can significantly change the fit of a regression line. This effect can even change the sign of the correlation. Lurking Variable - Answer️A variable, usually unobserved, that influences the association between the variables of primary interest summary or descriptive statistics - Answer️statistics to make the leap from historical data to story telling; use of DS and charts to summarize the data to identity trends Inferential Statistics - Answer️use of descriptive statistics of a sample to make estimates bout the population. Subject - Answer️the person or thing we are studying or measuring Variable - Answer️characteristic observed of the subject Examples of subject - Answer️People, STAT 201 students Example of Population - Answer️US population, all students in STAT classes at USC, the group we look at Examples of Variable - Answer️Height, gender Sample - Answer️the set of subjects that we have data for Population - Answer️the set of all subjects of interest Statistic - Answer️numerical summary of a sample; US alphabet to represent Statistic examples - Answer️Mean(