The official's truck in Fig. 2.2 is at x1 = 277 m at t1 = 16.0 s and is at x2 = 19 m at t2 = 25.0 s. (a) Sketch two different possible x-t graphs for the motion of the truck. (b) Does the average velocity during the time interval from t1 to t2 have the same value for both of your graphs? Why or why not?

Lecture 9: Estimating Proportions with Confidence 10.1: Overview of Confidence Intervals Confidence Intervals concept: Use sample data to estimate a population parameter Population (size N) = the whole group that we want to make conclusions on Parameter = summary about population Random sample of size n = a few units selected from population Statistic = summary about the sample Sample estimate = provides our best guess as to what is the value of the population parameter, but it is not 100% accurate. Concept: The value of the sample estimate will vary from one sample to the next. The values often vary around the population parameter and the standard deviation give an idea about how far the sample estimates tend to be from the true population proportion on average. The standard error of the sample estimate provides an idea of how far away it would tend to vary from the parameter value (on average). The general format for a confidence interval estimate is given by: Sample estimate ± (a few) standard errors 10.2: Confidence Interval for a Population Proportion p Probability that sample proportion will be within 2 standard deviations from the