appendix.qmd

# Appendix {.unnumbered}

## Solutions {.unnumbered}

### Exercise 1 Solution {.unnumbered}

[Exercise 1](02-working-with-data-sets.qmd#exercise-1)

1:

```stata
. sysuse lifeexp
(Life expectancy, 1998)

```

3:

```stata
. sysuse sandstone, clear
(Subsea elevation of Lamont sandstone in an area of Ohio)

```

or

```stata
. clear

. sysuse sandstone
(Subsea elevation of Lamont sandstone in an area of Ohio)

```

4:

If the working directory isn't convenient, change it using the dialogue box.
Then, `save sandstone`.

### Exercise 2 Solution {.unnumbered}

[Exercise 2](03-data-management.qmd#exercise-2)

1:

```stata
. webuse census9, clear
(1980 Census data by state)

```

2: Data is from the 1980 census, which we can see by the label (visible in
`describe, simple`). We've got two identifiers of state, death rate, population,
median age and census region.

3: Since there data has 50 rows, it's a good guess there are no missing sates.

4: Looking at `describe`, we see that the two state identifiers are strings, the
rest numeric.

5: `compress`. Nothing saved! Because Stata already did it before posting it!

### Exercise 3 Solution {.unnumbered}

[Exercise 3](03-data-management.qmd#exercise-3)

1:

```stata
. webuse census9, clear
(1980 Census data by state)

. save mycensus9, replace
(file mycensus9.dta not found)
file mycensus9.dta saved

```

The `replace` option is added in case I run it twice.

2:

```stata
. rename drate deathrate

. label variable deathrate "Death rate per 10,000"

```

3:

```stata
. tab region

     Census |
     region |      Freq.     Percent        Cum.
------------+-----------------------------------
         NE |          9       18.00       18.00
    N Cntrl |         12       24.00       42.00
      South |         16       32.00       74.00
       West |         13       26.00      100.00
------------+-----------------------------------
      Total |         50      100.00

. label list cenreg
cenreg:
           1 NE
           2 N Cntrl
           3 South
           4 West

. label define region_label 1 "Northeast" 2 "North Central" 3 "South" 4 "West"

. label values region region_label

. label drop cenreg

. label list
region_label:
           1 Northeast
           2 North Central
           3 South
           4 West

. tab region

Census region |      Freq.     Percent        Cum.
--------------+-----------------------------------
    Northeast |          9       18.00       18.00
North Central |         12       24.00       42.00
        South |         16       32.00       74.00
         West |         13       26.00      100.00
--------------+-----------------------------------
        Total |         50      100.00

```

4:

```stata
. save, replace
file mycensus9.dta saved

```

### Exercise 4 Solution {.unnumbered}

[Exercise 4](03-data-management.qmd#exercise-4)

```stata
. use mycensus9, clear
(1980 Census data by state)

```

1: Use `summarize` and `codebook` to take a look at the mean/max/min. No errors
detected.

2:

```stata
. codebook, compact

Variable   Obs Unique     Mean     Min       Max  Label
-------------------------------------------------------------------------------
state       50     50        .       .         .  State
state2      50     50        .       .         .  Two-letter state abbreviation
deathrate   50     30     84.3      40       107  Death rate per 10,000
pop         50     50  4518149  401851  2.37e+07  Population
medage      50     37    29.54    24.2      34.7  Median age
region      50      4     2.66       1         4  Census region
-------------------------------------------------------------------------------

```

`deathrate` and `medage` both have less than 50 unique values. This is due to
both being heavily rounded. If we saw more precision, there would be more unique
entires.

3:

```stata
. codebook, problems

Potential problems in dataset mycensus9.dta

               Potential problem   Variables
--------------------------------------------------
string vars with embedded blanks   state
--------------------------------------------------

```

This just flags spaces (` `) in the data. Not a real problem!

### Exercise 5 Solution {.unnumbered}

[Exercise 5](04-data-manipulation.qmd#exercise-5)

```stata
. use mycensus9, clear
(1980 Census data by state)

```

1:

```stata
. generate deathperc = deathrate/10000

. label variable deathperc "Percentage of population deceeased in 1980"

. list death* in 1/5

     +---------------------+
     | deathr~e   deathp~c |
     |---------------------|
  1. |       91      .0091 |
  2. |       40       .004 |
  3. |       78      .0078 |
  4. |       99      .0099 |
  5. |       79      .0079 |
     +---------------------+

```

2:

```stata
. generate agecat = 1 if medage < .

. replace agecat = 2 if medage > 26.2 & medage <= 30.1
(30 real changes made)

. replace agecat = 3 if medage > 30.1 & medage <= 32.8
(17 real changes made)

. replace agecat = 4 if medage > 32.8
(1 real change made)

. label define agecat_label 1 "Significantly below national average" ///
>                           2 "Below national average" ///
>                           3 "Above national average" ///
>                           4 "Significantly above national average"

. label values agecat agecat_label

. tab agecat, mi

                              agecat |      Freq.     Percent        Cum.
-------------------------------------+-----------------------------------
Significantly below national average |          2        4.00        4.00
              Below national average |         30       60.00       64.00
              Above national average |         17       34.00       98.00
Significantly above national average |          1        2.00      100.00
-------------------------------------+-----------------------------------
                               Total |         50      100.00

```

We have no missing data (seen with `summarize` and `codebook` in the previous
exercise) but it's good practice to check for them anyways.

3:

```stata
. bysort agecat: summarize deathrate

-------------------------------------------------------------------------------
-> agecat = Significantly below national average

    Variable |        Obs        Mean    Std. dev.       Min        Max
-------------+---------------------------------------------------------
   deathrate |          2        47.5     10.6066         40         55

-------------------------------------------------------------------------------
-> agecat = Below national average

    Variable |        Obs        Mean    Std. dev.       Min        Max
-------------+---------------------------------------------------------
   deathrate |         30    81.76667    9.761583         50         94

-------------------------------------------------------------------------------
-> agecat = Above national average

    Variable |        Obs        Mean    Std. dev.       Min        Max
-------------+---------------------------------------------------------
   deathrate |         17    91.76471    8.422659         73        104

-------------------------------------------------------------------------------
-> agecat = Significantly above national average

    Variable |        Obs        Mean    Std. dev.       Min        Max
-------------+---------------------------------------------------------
   deathrate |          1         107           .        107        107


```

We see that the groups with the higher median age tend to have higher
deathrates.

4:

```stata
. preserve

. gsort -deathrate

. list state deathrate in 1

     +--------------------+
     | state     deathr~e |
     |--------------------|
  1. | Florida        107 |
     +--------------------+

. gsort +deathrate

. list state deathrate in 1

     +-------------------+
     | state    deathr~e |
     |-------------------|
  1. | Alaska         40 |
     +-------------------+

. gsort -medage

. list state medage in 1

     +------------------+
     | state     medage |
     |------------------|
  1. | Florida    34.70 |
     +------------------+

. gsort +medage

. list state medage in 1

     +----------------+
     | state   medage |
     |----------------|
  1. | Utah     24.20 |
     +----------------+

. restore

```

5:

```stata
. encode state2, gen(statecodes)

. codebook statecodes

-------------------------------------------------------------------------------
statecodes                                        Two-letter state abbreviation
-------------------------------------------------------------------------------

                  Type: Numeric (long)
                 Label: statecodes

                 Range: [1,50]                        Units: 1
         Unique values: 50                        Missing .: 0/50

              Examples: 10    GA
                        20    MD
                        30    NH
                        40    SC

```