For the following data score represents the test score, prep_time represents the preparation time (in hours) and attend represents if a person attended the lectures.

score prep_time attend
1 0 none
5 5 some
10 10 all
9 14 all
4 3 some
7 5 all
11 14 all
8 8 all
3 6 some
2 5 none
  1. Draw a histogram for score using cutoffs 0,3,6,9,12.

  1. What is the score range?
## range = 10
  1. What are the means and standard deviations of score and prep_time?
## score mean = 6
## score sd = 3.496029
## prep_time mean = 7
## prep_time sd = 4.546061

4.You got 13 score on the test. Find z-score.

## [1] 2.002271
  1. If the histogram was symmetric and bell-shaped, would it be a good z-score?
## Yes, we are 2 sd above the average (and in top 2.5%)
  1. Draw score vs prep_time scatteplot. Do you think there is a relationship?

## looks like a positive trend
  1. What is the correlation between score and prep_time? Does this confirm your scatterplot findings.
## correlation = 0.8668997
## the correlation is close to 1 and positive => positive dependence
  1. Compute the distribution table (relative frequencies) for the attend variable.
## 
##  all none some 
##  0.5  0.2  0.3
  1. Draw a stacked diagram for attend.

  1. Find the average value of score and prep_time for each category of attend. (Try to interpret these values :)
attend score_mean score_prep_time
all 9.0 10.200000
none 1.5 2.500000
some 4.0 4.666667 
## people who attended many lectures have higher test scores
## people who attended less lectures tend to prepare less