Independent research from Global Insight has shown that Wal-Mart saves the average American

family $3,100 each year, no matter where they shop.

Source: WalMart TV commercial (2007)

“Wal-Mart is likely to have had a significant impact on price inflation across the MSAslargely for three main reasons. First, its sophisticated logistics and distributioninnovations have increased total factor productivity, lowering its overall cost structureand allowing Wal-Mart to provide its goods at lower prices. Second, Wal-Mart's integrated purchasing system and its sheer size has led its suppliers to offer significantvolume discounts, which Wal-Mart in turn has passed along to its consumers. Andthird, its lower prices have pressured its competitors to adopt more efficient processesand to lower their prices.

Our objective is to determine if Wal-Mart's presence has had an impact on measuredconsumer prices for urban consumers over the past 20 years. The CPI includes threebroad categories: durable goods (11%), non-durable goods (29%), and services (60%). If Wal-Mart has an impact on consumer prices, it would be on the first two categories. Consumer prices for services are dominated by rents, imputed rents, utilities, medical services, and transportation -- all areas outside of Wal-Mart's product offerings.”

The Price Impact of Wal-Mart: An Update Through 2006: Supplemental Report

“Once differences in consumer service prices are accounted for, we are able to explain nearly 89% of the variation in consumer price inflation across the MSAs by considering the variation in unemployment rate changes, high wage industry employment share growth, and electricity price growth.”

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0 0 1 1 1 2 2 2 2 2 2 2 3 3 3 33 3 4 4 4 4 4 4 4 5 5 5 6 7 8

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Number of Keys We HadMW class

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Number of Keys We’ve HadHistorically

For symmetric, unimodal data, you can use any of the three, for they are approximately equal.

Data that is skewed is so called because the mean is significantly different than the median or mode. For skewed data, you can safely use the median, or maybe mode (use care if considering the mean).

1) I gave an exam to 63 MTH 095 students.

2) Their average grade was 71.

3) Median grade was 78.

4) Minimum grade was no lower than 50.

5) Maximum grade was no higher than 100.

Draw a histogram that (roughly) indicates the statistics above. Here’s an axis for you to work off of…

For multimodal data, you should consider using the modes, as the median and/or mean might mislead, or be meaningless.

How about qualitative data (like hair color)?

What are the centers? Which

make sense to use?

Some (mis)uses of centers

1. The average annual snowfall in Bend is 33.8 inches.Source: Bend Chamber of Commerce (http://www.bendchamber.org/about/weather.html)

Some (mis)uses of centers

“Sunshine: Bend has the highest average number of sunny days in the state. Clear days average 158 days per year with an additional 105 days that are mostly sunny. Many of the remaining days provide substantial sunshine. Days that are totally cloudy do not often occur.”

2. Bend averages 300 sunny days a year.

Source: Bend Chamber of Commerce

Some (mis)uses of centers

3. “Think of how stupid the average person is, and realize half of them are stupider than that.”