How to create bottom 26% of the population

[Shikha Sharma]

Hi,

I have been using thus far xtile quin=mpce[aw=weight], n(5) to create bottom 20% of the population. How can we create the bottom 26% or bottom 33%?

Any help is appreciated

[Nick Cox]

The help for xtile tells you about other commands in the same territory. So for example you can get estimates of the 26th and 33rd percentiles.

.

 sysuse auto, clear
(1978 Automobile Data)

. _pctile mpg, p(26 33)

. ret li

scalars:
                 r(r1) =  18
                 r(r2) =  18

. quantile mpg, yline(18)

The example is instructive. The graph shows that ties can mean that returning the same result for different percentiles can be entirely reasonable.

See also the pctile() function of egen.

[Shikha Sharma]

Thank you ever so much. Just to clarify-- with r(r1)=18, any observation for mpg less than equal to 18 shall be my target group for bottom 26%?

[Nick Cox]

Indeed. Also 18 is reported as every percentile from 25 to 36. Your own data may be less awkward. .

sysuse auto, clear
numlist "1/99"
_pctile mpg , p(`r(numlist)')
forval j = 1/99 {
    di `j' "{col 7}" r(r`j')
}


1     12
2     12
3     14
4     14
5     14
6     14
7     14
8     14
9     14
10    14
11    15
12    15
13    15
14    16
15    16
16    16
17    16
18    16
19    17
20    17
21    17
22    17
23    17
24    17
25    18
26    18
27    18
28    18
29    18
30    18
31    18
32    18
33    18
34    18
35    18
36    18
37    19
38    19
39    19
40    19
41    19
42    19
43    19
44    19
45    19
46    19
47    19
48    20
49    20
50    20
51    20
52    21
53    21
54    21
55    21
56    21
57    21
58    21
59    22
60    22
61    22
62    22
63    22
64    22
65    23
66    23
67    23
68    23
69    24
70    24
71    24
72    24
73    24
74    24
75    25
76    25
77    25
78    25
79    25
80    25
81    25
82    26
83    26
84    26
85    26
86    28
87    28
88    28
89    28
90    29
91    30
92    30
93    30
94    31
95    34
96    35
97    35
98    35
99    41