Quiz 8.1

For the distribution in the following table, what is the percentile rank for X = 32?​ X c% 30-34 100% 25-29 90% 20-24 60% 15-19 20%

34.5 --> 100% 32 --> ? % 29.5 --> 90% Distance between X values: 34.5 - 29.5 = 5 Distance between percentile: 100-90 = 10 Therefore, 5 points distance is equivalent to 10 percentile distance. What is the distance between 34.5 and 32? 34.5-32 = 2.5 What percentile distance does 2.5 point distance correspond to? 2.5/5 * 10 = 0.5 * 10 = 5 What is the percentile rank that is 5 percentile below 100? 100-5 = 95

If a frequency distribution is shown in a bar graph, what scale was used to measure the scores?​

Bar graphs show non-computable values that are usually on nominal or ordinal scale (GW pg 45)

For the scores shown in the accompanying stem and leaf display, Figure 2-3, what is the highest score in the distribution?​

Look first for the highest stem number (8) and then the highest leaf number (4) in association with the specific stem

For the distribution in the accompanying graph, Figure 2.1, what is the value of ΣX?​

Sum of X = (1*1) + (2*2) + (3*4) + (4*2) + (5*1) = 30

The normal distribution is ____.​

Symmetry = Normal (GW pg 48)

If the following scores were placed in a stem and leaf display, how many leaves would be associated with a stem of 6?​ Scores: 26, 45, 62, 11, 21, 55, 66 64, 55, 46, 38, 41, 27, 29 36, 51, 32, 25, 34, 44, 59​

There are three scores that begin with 6 (62, 64, 66). Therefore, there are going to be three leaves associated with the stem of 6.

The students in a psychology class seemed to think that the midterm exam was very easy. If they are correct, what is the most likely shape for the distribution of exam scores?​

This would mean that most students would have a high score, and only a few people would have a low score (negative skew)

For the distribution in the following table, what is the percentile rank for X = 8.5?​ X c% 9 100% 8 80% 7 50% 6 25%​

You can use interpolation to calculate the answer here, but really you can just eyeball the choices and pick the right answer. 9 -->100% 8 --> 80% This can be re-written as the following (using the idea of real limits): 9.5 -->100% 8.5 --> 80% When you encounter a problem like this one, work from the top. What corresponds to 100%? It's the real-upper-limit of the correspond X value, which is 9.5 in this case. After that, simply work your way down to determine the real-upper-limit of every X-value. In this case, 8.5 corresponds to 80%