Bias Can you avoid it? Common forms of bias to avoid.

Survey outcome Total Stars Awarded this year Average Reading age Boys1016 years 7 months Girls1967 years 1 months Girls clearly outperform boys in performance as shown by the number of stars awarded. Girls are also more advanced in their reading skills. Reality – there are only 10 boys in this class, 22 girls, of which 16 girls have birthdays in September, October and November. All bar one of the boys have birthdays after March. Girls clearly outperform boys in performance as shown by the number of stars awarded.

Jargon The standard deviation of the attendance from the first school is worse than the variance in the second school 10% of that 80% of poor readers could not punctuate correctly The chi-squared index of 5.5 shows errors in the marking scheme.

Sample Size = 4

Mean, Mode, Median and Range