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Unformatted text preview: Math Review for ECO220Y: PART 1 of 2 For success in our course it is important that you have the skills needed to solve the problems in both Part 1 and Part 2 of this Math Review. If you find these questions easy then you do not need to spend much time on this. However, if your skills are rusty or missing it is important that you work to get caught up. Both parts of this Math Review are here to help you. Additionally our Teaching Assistants (TA’s) have office hours should you run into difficulty when working through these problems. 1 Percentages A percent is a fraction, ratio, or proportion multiplied by 100. A percentage point is a unit expressing the difference between two percentages. 1. Suppose that the interest rate is currently 2.76%. (a) What would the new interest rate be if the bank increased it by 1 percentage point? (b) What would the new interest rate be if the bank increased it by 1 percent? 2. Consider a data set that contains 225 observations obtained from a survey of individuals. Three of the variables are gender, whether the individual is retired, and income. (a) If 56 of the observations are marked female, what percent of the data is female? (b) If the remaining observations are marked male, what percent of the data is male? (c) If 16% of the observations are marked retired, what number of observations is retired? (d) If 0.5% of the observations are marked retired, what number of observations is retired? (e) How many more individuals would you need to survey to increase the sample size by 10%? (f) How many observations would you have left if you needed to discard 20% of the data because it was incorrectly entered? (g) If 16% of the observations are marked retired, how many more retired individuals would you need to survey to increase the percent retired in the data by 4 percentage points? 1 (h) If 16% of the observations are marked retired, how many more retired individuals would you need to survey to increase the proportion retired in the data by 4 percent? (i) Suppose 12% of the observations are missing a value for income. (This often happens in realworld data as some people do not feel comfortable revealing their income for a survey.) i. How many individuals refused to reveal their income? ii. Suppose that in the entire data set 48% had income less than or equal to $50,000 and 40% had income above $50,000. Of those that responded to the income question, what percent had income less than or equal to $50,000? Above $50,000? 2 Equation of a Line A line, which completely summarizes the linear relationship between x and y, is often written in terms of the yintercept a and the slope b . y = a + bx (1) The intercept ( a ) is the value of y when x is equal to zero....
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This note was uploaded on 04/10/2010 for the course ECO ECO220 taught by Professor Atamazaheri during the Spring '09 term at University of Toronto.
 Spring '09
 ATAMAZAHERI
 Economics

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