HOMEWORK 1: Basic Statistics1.
Using the Calcium Database (homework 1 data). The data were collected to
investigate whether increasing calcium intake reduces blood pressure. Twenty-one
people participated in this experiment, where 10 of them took a calcium supplement for
12 weeks, while the remaining 11 received a placebo. The blood pressure of each
subject was measured before and after the 12-week period. (2 points)
Steps:
Download the CSV information that was provided into SPS.
a)
What kind of variables are Begin and End and what kind of scale are they
following? (0.5 points)
b)
Plot the frequency histogram of the variables Begin and End. Compare the two
histograms in terms of their central tendency and the form of their histogram not
only in statistical terms but also the applied meaning of the differences in the
shapes. (0.5 points)
Steps to get the graphs:
Click graphs, then histograms, and then insert either end or begin in the variables section to get
one of the graphs.
c)
Plot the box plot of both variables, Begin and End. Highlight where the Quartile
1 is and specify if there are any outliers. (0.5 points)
Steps:
On the top, open up graphs and press boxplot. Then, click “summaries of separate variables” and
drag each variable to the variables box. Start with the “begin”, then when that graph is collected,
remove it and add in the “end”.
d)
Obtain the mean, median, and standard deviation of each variable and each
variable by treatment. How do they match with your explanation in c)? (0.5 points)
Steps:
At the top, press analyze descriptive statistics, then descriptives and move each one,
one at a time in the variables box.
2.
Probability (3 points)
a)
What kind of distribution would you say that Begin and End follow? (0.6
points)
b)
What is the probability of having a blood pressure lower than 100 at the
end of the experiment (hint: assuming a normal distribution)? (0.6 points)
c)
What is the probability of having a blood pressure higher than 120 at the
beginning of the experiment? (0.6 points)
d)
What would be the standardized value of 100 at the end of the experiment?
(0.6 points)
e)
Considering that Begin follows a normal distribution, generate 5 values
that follow the same mean and standard deviation (these values should be
generated from SPSS or R function). (0.6 points) (Note: we have not taught this in
the class. Feel free to google to find out!)
