sas 强人帮我看看这个怎么写 为什么我怎么写 Y都是错的呢 5555555

shiyiming

During World War II German submarines (U-boats) patrolled the Atlantic ocean looking for enemy ships to sink. Suppose a U-boat has 16 torpedoes (underwater missiles) to start off with when they left their U-boat pens in occupied France.
Suppose that each U-boat attack on an enemy ship uses 1 torpedo with probability 0.7, 2 torpedoes with probability 0.2, and 3 torpedoes with probability 0.1. (This is because big targets may require more hits and some torpedoes miss their target etc.)
We wish to estimate Y = the total number of enemy ships that will be attacked until the U-boat has run out of torpedoes. This includes the last ship even if there aren‟t enough torpedoes to sink it.
(a) Write a SAS program to simulate the distribution of Y. Perform 1000 simulations. If you wish to write a SAS macro then you may assume that the code below has been given to you and your code to be inserted at the position of the /*******/. Alternatively, you could attempt to do the simulation entirely within a data step.

%MACRO uboat(numiters);
%DO iter=1 %TO &numiters;
/**********/
/* Append results to dataset simout */ DATA simout; %IF &iter=1 %THEN %DO; SET sim; %END; %ELSE %DO; SET simout sim; %END; RUN; %END; /* End of %DO loop */
PROC MEANS DATA=simout; VAR Y; TITLE "Summary statistics of the ships attacked; &numiters iterations"; RUN;
PROC FREQ DATA=simout;
TABLES Y; RUN;
%MEND(uboat);
%uboat(1000);
(b) What statistical and/or practical assumptions have you made in (a)?
(c) Suppose you run your program (and it works) and your output is given below. Estimate E(Y).
Summary statistics of the ships attacked; 1000 iterations
The MEANS Procedure
Analysis Variable : Y
N Mean Std Dev Minimum Maximum
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1000 11.6720000 1.5750863 7.0000000 16.0000000
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Summary statistics of the ships attacked; 1000 iterations
The FREQ Procedure
Cumulative Cumulative
Y Frequency Percent Frequency Percent
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7 2 0.20 2 0.20
8 15 1.50 17 1.70
9 71 7.10 88 8.80
10 146 14.60 234 23.40
11 212 21.20 446 44.60
12 260 26.00 706 70.60
13 163 16.30 869 86.90
14 99 9.90 968 96.80
15 30 3.00 998 99.80
16 2 0.20 1000 100.00
(d) At one time during the course of the war there were 200 U-boats operating in the Atlantic. Suppose they all attacked one (different) ship each on the same day, and that all U-boats had at least 3 torpedoes each initially. On average, how many torpedoes in total would be used that day? You may assume the above assumptions hold.

shiyiming

[code:33zncy6s]
ships=0;
missiles=0;
do until (missiles>=16);*number of missiles may be presumably more than 16,that should be Okay;
  ran=ranuni(0);  
  missiles+ifn(ran<=0.7,1,ifn(ran<=0.9,2,3));*at last attack, u-boat may need more missiles than number of missiles left,but that still counts;
  ships+1;
end;
[/code:33zncy6s]

*i dont have SAS at home thus not able to test it