The bar graph depicts how much below average are the Reliability-Durability GPAs of 1985's 30 lowest autos.

Computations

To compute the reliability-durability grade point average of the Model Year 1985 cars, Consumer Reports' reliability ratings for the age ranges 4-to-5 years and 5-to-6 years are used. The April 1990 and 1991 issues of Consumer Reports are the sources of CR's reliability ratings.

CR's ratings are converted to numerical values following the standard academic pattern: a grade point of 4.0 (an A) is accorded a rating of Much Better Than Average, a 3.0 (a B) is accorded a rating of Better Than Average, a 2.0 (a C) is accorded a rating of Average, a 1.0 (a D) is accorded a rating of Below Average, and a 0 (an F) is accorded a rating of Much Below Average.

Then, for each age range, the grade point of CR's overall reliability rating is weighted 2/3 and the average of the grade points of the category ratings is weighted 1/3.

Finally, the average for the two age ranges is taken.

The Chevrolet Sportvan Inline 6, Mercury Capri 4-cylinder, and Cadillac Cimarron 4-cylinder offered only one age range of data.

For more discussion regarding these automobiles and this particular auto quality measure, see http://CarsOnInfo.net/20WorstCarsOfModelYear1985.aspx or http://www.CarQualityInfo.net/reliability-durability-gpas/20-worst-cars-of-model-year-1985 .