61 lines
2.8 KiB
JavaScript
61 lines
2.8 KiB
JavaScript
var test = require('tape');
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var ss = require('../');
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test('natural distribution and z-score', function(t) {
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test('normal table is exposed in the API', function(t) {
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t.equal(ss.standard_normal_table.length, 310);
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t.equal(ss.standard_normal_table[0], 0.5);
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t.end();
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});
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test('P(Z <= 0.4) is 0.6554', function(t) {
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// Taken from the examples of use in http://en.wikipedia.org/wiki/Standard_normal_table
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t.equal(ss.cumulative_std_normal_probability(0.4), 0.6554);
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t.end();
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});
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test('P(Z <= -1.20) is 0.1151', function(t) {
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// Taken from the examples of use in http://en.wikipedia.org/wiki/Standard_normal_table
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t.equal(ss.cumulative_std_normal_probability(-1.20), 0.1151);
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t.end();
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});
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test('P(X <= 82) when X ~ N (80, 25) is 0.6554', function(t) {
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// Taken from the examples of use in http://en.wikipedia.org/wiki/Standard_normal_table
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// A professor's exam scores are approximately distributed normally with mean 80 and standard deviation 5.
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// What is the probability that a student scores an 82 or less?
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t.equal(ss.cumulative_std_normal_probability(ss.z_score(82, 80, 5)), 0.6554);
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t.end();
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});
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test('P(X >= 90) when X ~ N (80, 25) is 0.0228', function(t) {
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// Taken from the examples of use in http://en.wikipedia.org/wiki/Standard_normal_table
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// A professor's exam scores are approximately distributed normally with mean 80 and standard deviation 5.
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// What is the probability that a student scores a 90 or more?
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t.equal(+(1 - ss.cumulative_std_normal_probability(ss.z_score(90, 80, 5))).toPrecision(5), 0.0228);
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t.end();
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});
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test('P(X <= 74) when X ~ N (80, 25) is 0.1151', function(t) {
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// Taken from the examples of use in http://en.wikipedia.org/wiki/Standard_normal_table
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// A professor's exam scores are approximately distributed normally with mean 80 and standard deviation 5.
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// What is the probability that a student scores a 74 or less?
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t.equal(ss.cumulative_std_normal_probability(ss.z_score(74, 80, 5)), 0.1151);
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t.end();
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});
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test('P(78 <= X <= 88) when X ~ N (80, 25) is 0.6006', function(t) {
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// Taken from the examples of use in http://en.wikipedia.org/wiki/Standard_normal_table
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// A professor's exam scores are approximately distributed normally with mean 80 and standard deviation 5.
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// What is the probability that a student scores between 78 and 88?
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var prob88 = ss.cumulative_std_normal_probability(ss.z_score(88, 80, 5)),
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prob78 = ss.cumulative_std_normal_probability(ss.z_score(78, 80, 5));
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t.equal(+(prob88 - prob78).toPrecision(5), 0.6006);
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t.end();
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});
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t.end();
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});
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