Generating mean of a score within bands of age

[Alan Jeddi]

Hi everybody,

I have 2 variables which are measured continuously, "LOP" and "Age"
I would like to split the age into 5 year age bands.

Then, I would like to calculate the mean age and mean LOP within each age band.
(ie, I would like to know the mean age within each Age Band, and its corresponding mean LOP)

Then, I would like to plot each of these, with their corresponding standard errors, and then fit a line of best fit between these points.

I have absolutely no idea how to do this, and I am very lost. Any help from anybody would be extremely appreciated.

Thank you.

[Carlo Lazzaro]

Alan:
you might be interested in something along the following lines:

. sysuse auto.dta
(1978 Automobile Data)

. reg price i.rep78

      Source |       SS           df       MS      Number of obs   =        69
-------------+----------------------------------   F(4, 64)        =      0.24
       Model |  8360542.63         4  2090135.66   Prob > F        =    0.9174
    Residual |   568436416        64     8881819   R-squared       =    0.0145
-------------+----------------------------------   Adj R-squared   =   -0.0471
       Total |   576796959        68  8482308.22   Root MSE        =    2980.2

------------------------------------------------------------------------------
       price |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
       rep78 |
          2  |   1403.125   2356.085     0.60   0.554    -3303.696    6109.946
          3  |   1864.733   2176.458     0.86   0.395    -2483.242    6212.708
          4  |       1507   2221.338     0.68   0.500    -2930.633    5944.633
          5  |     1348.5   2290.927     0.59   0.558    -3228.153    5925.153
             |
       _cons |     4564.5   2107.347     2.17   0.034     354.5913    8774.409
------------------------------------------------------------------------------


. margins i.rep78

Adjusted predictions                            Number of obs     =         69
Model VCE    : OLS

Expression   : Linear prediction, predict()

------------------------------------------------------------------------------
             |            Delta-method
             |     Margin   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
       rep78 |
          1  |     4564.5   2107.347     2.17   0.034     354.5913    8774.409
          2  |   5967.625   1053.673     5.66   0.000     3862.671    8072.579
          3  |   6429.233   544.1145    11.82   0.000      5342.24    7516.227
          4  |     6071.5   702.4489     8.64   0.000     4668.197    7474.803
          5  |       5913   898.5756     6.58   0.000     4117.889    7708.111
------------------------------------------------------------------------------

. marginsplot

  Variables that uniquely identify margins: rep78

.

[Alan Jeddi]

Thanks Carlo, this is the exact type of graph I am looking for!

I managed to sort it all out; do you know if there is a way to show this main line, as well as seperate lines, one for males and one for females?

[Carlo Lazzaro]

Alan:
I find difficult to reply without taking a look at what you typed and what Stata gave you back.

[Alan Jeddi]

Alan:
I find difficult to reply without taking a look at what you typed and what Stata gave you back.

Hi Carlo,
My apologies. I generated a new variable, age5, which is my original age cut into 5 year bands, using the egen.
My code for the plot was:

regress iopcc_out i.age5 sex
margins i.age5, by(i.sex)
marginsplot

regress iopcc_out i.age5
margins i.age5
margins plot

I end up producing the following graphs.
This is in the ballpark of what I want, but it seems like the margins when stratified by sex are identical so I think I must have done something incorrectly.
What I am really hoping to have is a single chart, with 3 lines (one overall, one for females and one for males)..

[Alan Jeddi]

charts