Statistics

Tacoma Gas Pricing Random Sampling (2.50, 2.67, 3.00, 2.75, 3.50, 2.95, 3.00, 2.50, 2.50, 5.00) Prices sampled at ten different stations. This chart illustrates a random sampling of gas prices taken from 10 different gas stations in the Tacoma, Washington area. Using this illustration, we find that there are similar gas prices at many of the stations.

Mode, Median, and Mean The Mode – most often occuring number in a series of numbers. 2.50 The Median – The middle number. 3.75 The Mean – an average of a set of numbers. (found by adding the numbers together, and then dividing the sum by the number or set of numbers) In this case; 3.03 Range = 2.5 to 5.0 With the sample data on the previous slide, we can find a range, a mean, a median, and a mode. Each of these numbers has a different calculation. The mode is the number that occurs most often. In the data sample we can see that the number occurring most frequently is 2.50. The median is the number that is at the center of the data set or the middle of the data range. In this case, the median is 3.75. This does not however, represent the average price of a gallon of gas. To find this, we need to discover the mode. This number is found by dividing the sum of the data sample by the amount of data points within that sample. This is how we arrive at 3.03 per gallon. The range is the easiest number to discover. It consists of the highest number in the data set and the lowest number in the data set. The range for this example is 2.50 to 5.00.

Which Number do We Want? Depends on: Desired outcome Data sample Method of calculation Depending on the answer you want to find, you can use any of the methods for analyzing the data you have. The best way to analyze the data given here, is to find the median. This is because we want to know what the average consumer is going to spend on gas when making a decision to purchase a conventional vehicle, or a hybrid vehicle. With the median gas cost, we can then determine how much will be spent throughout the year on gas, and what the savings might be if we were to purchase a hybrid. For this case, we want the median, or average cost.

Why Median? Median gives us an average cost Median is easy to calculate Median is half way there The median can give us an idea of what the average cost of a gallon of gas is in a particular geographic region. It provides the average of a data set. With the median, when there are not extremes in data samples, it gives us a very accurate average of any data set. The median is perhaps the easiest number to calculate when dealing with a data set. It consists of adding the numbers together in a data set and obtaining the sum. The sum is then divided by the number of entries the data set contains. This gives you the median. Low end data High end data Median