51 ttl

What are the chances that a person picked at random will have a score of 9 or above?

What are the chances that a person picked at random will have a score above 9? 3/51 or 6%

What are the chances that a person picked at random will have a score between 4 & 7?

31/51 or 61%

Random Number Table

Total = 51 a 2-digit number – therefore we break the random numbers into groups of two digits

Measure of spread A formal way to describe how spread out data is, is by calculating the average distance from the individual measurements to the overall mean. The more spread out the data is, the larger the average distance the data is to the mean. We call that average difference the Standard Deviation.

Empirical Rule In statistics, the empirical rule states that nearly all values lie within 3 standard deviations of the mean in a normal distribution. – About 68% of the values lie within 1 standard deviation of the mean. – About 95% of the values lie within 2 standard deviations of the mean. – Nearly all (99.7%) of the values lie within 3 standard deviations of the mean.

Mean and Standard Deviation Arithmetic mean = average = sum/number of observations Standard Deviation = average distance from the mean = a measure of how spread out the data is.

Standard Deviation The symbol for Standard Deviation is σ (the Greek letter sigma). This is the formula for Standard Deviation:

It is easy ParticipantScoreMeanScore – Mean (difference) (Mean – Score) Sqd (-1.8)(-1.8) = ttl /10 (56) = SD 2.36