You are here

Group Exercise: Standard Scores

Calculate the standard score (Z) and determine the probability for the following conditions. The mean hourly wage for New Yorkers with a college degree is $18.25. The population standard deviation is $11.80. Each group will demonstrate their work on the whiteboard.

You can compute the area under the normal curve here: http://www.stat.berkeley.edu/~stark/SticiGui/Text/clt.htm#normal_curve

1. What is the probability of drawing a person at random whose wage is below $15?
2. What is the probability of drawing a person at random whose wage is above $25?
3. What is the probability of drawing a person at random whose wage is between $19 and $23?
4. What is the probability of drawing a person at random whose wage is between $14 and $18?
5. What is the probability of drawing a person at random whose wage is between $20 and $22?

Comments

z = 25-18.25/11.8
z=0.572

Therefore, the probability of drawing a person at random whose wage is above $25 is 28.4%.

Probability of drawing a person at random whose wage is between 14$ and 18$ is 13.22%.

The probability of drawing a person at random whose wage is between $20 and $22 is 6.55%.

z = 20 - 18.25/11.80 = 0.148
z = 22 - 18.25/11.80 = 0.317

Probability = 0.655

z=(25000-22500)/1725
> z=(15-18.25)/11.80
-0.2754
The probability of someone earning less than $15 an hour is 39.17%

z=.064
z=.403
Probability: 13.1