Misleading Graphs and Statistics Arizona State Standard Objective

Misleading Graphs and Statistics Arizona State Standard:

Objective I will recognize misleading pictographs and bar graphs. I will recognize and correct misleading line graphs.

Questions to Ask When Looking at Data and/or Graphs n Is the information presented correctly? n Is the graph trying to influence you? n Does the scale use a regular interval? n What impression is the graph giving you?

What makes a graph misleading? n Irregular Intervals n Break in the scale (horizontal/vertical) n Distorted data *Over/Under-sized bars/pictures n Biased Title n Vertical Axis starting @ something other than zero

Why is this graph misleading? This title tells the reader what to think (that there are huge increases in price). The scale moves from 0 to 80, 000 in the same amount of space as 80, 000 to 81, 000. The actual increase in price is 2, 000 pounds, which is less than a 3% increase. The graph shows the second bar as being 3 times the size of the first bar, which implies a 300% increase in price.

A more accurate graph: An unbiased title A scale with a regular interval. This shows a more accurate picture of the increase.

Why is this graph misleading? The scale does not have a regular interval.

Graphs can be misleading in the news. n The margin of error is the amount (usually in percentage points) that the results can be “off by. ” n Be wary of data with large margins of error.

From CNN. com

Problems: The difference in percentage points between Democrats and Republicans (and between Democrats and Independents) is 8% (62 – 54). Since the margin of error is 7%, it is likely that there is even less of a difference. n The graph implies that the Democrats were 8 times more likely to agree with the decision. In truth, they were only slightly more likely to agree with the decision. n The graph does not accurately demonstrate that a majority of all groups interviewed agreed with the decision. n