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 one year ago
The lengths of the eggs of a species of bird are roughly normally distributed, with a mean of 32 mm and an SD of 1.2 mm.
Approximately 50% of the eggs have lengths in the range 32 mm plus or minus ____________ mm.
 one year ago
The lengths of the eggs of a species of bird are roughly normally distributed, with a mean of 32 mm and an SD of 1.2 mm. Approximately 50% of the eggs have lengths in the range 32 mm plus or minus ____________ mm.

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ZeHanz
 one year ago
Best ResponseYou've already chosen the best response.2This is what you need:dw:1363253506385:dw

ZeHanz
 one year ago
Best ResponseYou've already chosen the best response.2To find out what the number on the dots is, you have to use a table or a graphical calculator like the TI84. These have a builtin function that accepts a probability that is cumulative from the left:dw:1363253885929:dw

ZeHanz
 one year ago
Best ResponseYou've already chosen the best response.2In your case, because of the given middle 50%, the parts left and right of it, are 25%, so the cumulative probability (from the left) is 75%. Suppose L is the egglength, then you would write it in mathematical notation as follows: \(P(L<0.75~\mu =32,~\sigma=1.2)=x\). On the TI84, you need the invNormfunction. Type in: \(invNorm(0.75, 32,1.2)\). Result: 32.81. Now, because of the symmetry of the normal distribution, you can answer the question.

ZeHanz
 one year ago
Best ResponseYou've already chosen the best response.232 mm plus or minus ____________ mm. Because we've found the "plus" side of the 50% area to be 32.81 mm, 0.81mm has been added. Your answer will be 0.81. But: it is not quite clear what number of decimals are to be given, so it could also be 0.8 or 0.809. The calculator doesn't care: it gave me 32.8093877 as result from the invNorm function...

Directrix
 one year ago
Best ResponseYou've already chosen the best response.1I worked by hand using the tables and got 32 +/ .804. I did not interpolate. The standard deviation is tight about the mean. Somehow the answer did not feel right but I think it is okay.

Directrix
 one year ago
Best ResponseYou've already chosen the best response.1I had 32.238 < 32 < 32.838 as the 50% of egg lengths range. But, that is not the question.

ZeHanz
 one year ago
Best ResponseYou've already chosen the best response.2I think in general the answer of the calculator is more accurate than that of a table, but there is no need to give many decimals if the standard deviation has only 1...

Directrix
 one year ago
Best ResponseYou've already chosen the best response.1@Nurali > My @signal does not work. Send a web mail or note message if you need my help. Unless I happen to see that you called me, I don't know.

Directrix
 one year ago
Best ResponseYou've already chosen the best response.1Oh, yes, I agree @ZeHanz. I had to go with the tools I had here.

ZeHanz
 one year ago
Best ResponseYou've already chosen the best response.2@jishan: what do you mean?
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