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Coding Exercise (Answer)
​
Exercise 1

Answer:
Proc Univariate Data=AQI;
Var AQI;
​Run;

​The requested statistics are:
  • Mean: 110.47
  • Mode: 11
  • Median: 85
  • Variance: 9550
  • Range: 462

The Median AQI in the month of September is 85 µg/m³.
​
​
Exercise 2
Answer:
Proc Univariate Data=AQI normal plots;
Var AQI;
histogram;
Run;

Numerical Method:
All of the p-values are less than 0.05. There is sufficient evidence to suggest that the distribution is not normally distributed.

Graphical method:
The histogram clearly shows a declining trend of the AQI. The distribution is not normally distributed at all.


​
Exercise 3

Answer:
Proc Means Data=AQI noprint;
Var AQI;
Class Hour;
Output Out=AQIHour Mean=Mean STD=STD;
Run;

Proc Sort Data=AQIHour;
By descending Mean;
Run;

Look at the AQIHour data set.

The 5 highest AQI are reported at:
  • Hour 23 at 125.64
  • Hour 0  at 124.42
  • Hour 22 at 123.22
  • Hour 1  at 122.87
  • Hour 2  at 122.06

The air pollution is definitely at its worst during mid-night.


Exercise 4

Answer:
Proc Freq Data=Repair;
Table Brand / plots=freqplot;
Run;

Lenovo has the largest number of defective laptops between 2012 to 2015 at 153 pieces.


Exercise 5

Answer:
No. The result did not take into consideration the total number of laptops in the region.

For example, Lenovo might not have the highest defective rate if it has 5 times the users than all the other brands.


Exercise 6

Answer:
Proc Format;
Value period 1 = "< 1 year"
             2 = "Between 1-2 year"
             3 = "Between 2-3 year"
             4 = "> 3 years";
Run;

Data Repair2;
Set Repair;
** Correct Incomplete Date **;
Format Purdatenum date9. Period Period.;
If length(Purdate) = 9 then PurdateNum = input(Purdate, date9.);
else if length(Purdate) = 7 then PurdateNum = input("15" || Purdate, date9.);
else if length(Purdate) = 4 then PurdateNum = input("15JUN" || Purdate, date9.);

Diff = Repdate - PurdateNum;

if Diff <365 then Period = 1;
else if Diff <730 then Period = 2;
else if Diff <1095 then Period = 3;
else if Diff <1460 then Period = 4;

Run;


Exercise 7

Answer:
Proc Freq Data=Repair2;
Table Period / nocum;
Run;

The majority of the laptop starts experiencing problem between 1-2 years after the initial purchase.


Exercise 8

Answer:
Proc Freq Data=Repair2;
Table Brand * Parts;
Run;

Out of the 72 defective laptops from Dell, only 6 of them are related to their software (8.33%). It is definitely a strength of their computer.

On the other hand, Dell's laptop is weak in its keyboard, with 26 defective laptops related to their keyboard (36.11%).


Exercise 9

Answer:
Proc Means Data=Repair2;
Var Cost;
Class Brand;
​Run;

All of the brands have comparable repair cost, with Lenovo having the highest average repair cost at $230.


Exercise 10

Answer:
ODS PDF file='/folders/myfolders/analysis.pdf';
proc means data=profile;
var age height weight income premium;
run;

proc freq data=profile;
table gender edu race region;
run;
ods pdf close;
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