Need to find probability

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Stirling Ellis
Stirling Ellis 2022-4-27
评论： Stirling Ellis 2022-4-27
Hello, my goal is to find the probability a piece of wood has a module of elasticity greater than 2.00e6. My code is below
%Equation and initialized variables
mean = 1930000;
standardDeviation= 64000;
fx = @(x) (1/(standardDeviation * sqrt(2 * pi))) * exp(-((x - mean).^2 / (2 * standardDeviation ^ 2)));
xmin = mean - 3*standardDeviation;
xmax = mean + 3*standardDeviation;
plot(xmin:xmax,fx(xmin:xmax),'o--b')
%Value of Normal PDF
y = pdf('Normal',xmin:xmax,mean,standardDeviation);
This code manages to yield a normal distribution plot. My goal is to try and find what percentage of these values in the plot are above the elasticty of 2.00e6. Thank you so much in advance!

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采纳的回答

Image Analyst
Image Analyst 2022-4-27
编辑：Image Analyst 2022-4-27
Try this:
% Equation and initialized variables
mean = 1930000;
standardDeviation= 64000;
fx = @(x) (1/(standardDeviation * sqrt(2 * pi))) * exp(-((x - mean).^2 / (2 * standardDeviation ^ 2)));
xmin = mean - 3*standardDeviation;
xmax = mean + 3*standardDeviation;
x = xmin:xmax;
subplot(2, 1, 1);
plot(x,fx(x),'b-', 'LineWidth', 3);
grid on;
xline(2e6, 'Color', 'r', 'LineWidth', 2);
%Value of Normal PDF
y = pdf('Normal',xmin:xmax,mean,standardDeviation);
cdf = cumsum(y);
% Normalize to 0-100%
cdf = 100 * cdf / cdf(end);
subplot(2, 1, 2);
plot(x, cdf, 'b-', 'LineWidth', 2);
xline(2e6, 'Color', 'r', 'LineWidth', 2);
yticks(0:10:100)
grid on;
% Find value where value is 2e6
index = find(x >= 2e6, 1, 'first')
prob = cdf(index)
yline(prob, 'Color', 'r', 'LineWidth', 2)
message = sprintf('The probability of 2e6 or less is %f %%.\n', prob)
title(message)
uiwait(helpdlg(message));

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