# Khan/khan-exercises

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 e27b12e New exercise: Z-scores 2: Reading a z-table smenks13 authored Mar 6, 2012 1 aa6f903 Replace toFixed with localeToFixed xymostech authored Jun 3, 2013 2 ced362c Run the exercise cleaner. jeresig authored Apr 23, 2013 3 4 24b734a Clean up the titles of the HTML files. jeresig authored Apr 16, 2013 5 Z scores 2 ac1415e Use requirejs for module loading spicyj authored Mar 5, 2014 6 e27b12e New exercise: Z-scores 2: Reading a z-table smenks13 authored Mar 6, 2012 7 8 9fdecff beneater authored Apr 16, 2012 9
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87b4394 Fix a bunch of nits from math questions feedback beneater authored Nov 7, 2013 11
9fdecff beneater authored Apr 16, 2012 12
13 randRange(0, 9) 14 randRange(0, 9) 15 roundTo(2, randRange(0, 2) + ROW_INDEX / 10 + COL_INDEX / 100) 16 randRange(70, 90) 17 randRange(2, 6) d5bdea4 mauk81 authored Sep 19, 2013 18 localeToFixed(GRADE - ZSCORE * STDDEV, 2) 9fdecff beneater authored Apr 16, 2012 19 20 (function() { 21 var rowNames = []; 22 for(var i = floorTo(0, ZSCORE); i < (floorTo(0, ZSCORE) + 1); i += 0.1) { aa6f903 Replace toFixed with localeToFixed xymostech authored Jun 4, 2013 23 rowNames.push(localeToFixed(i, 1)); 9fdecff beneater authored Apr 16, 2012 24 } 25 return rowNames; 26 })() 27 d5bdea4 mauk81 authored Sep 19, 2013 28 [.00, .01, .02, .03, .04, .05, .06, .07, .08, .09] 9fdecff beneater authored Apr 16, 2012 29 30 (function() { 31 var zGrid = []; 32 for (var i = 0; i < ROWS.length; i++) { 33 var zRow = []; 34 for (var j = 0; j < COLUMNS.length; j++) { d5bdea4 mauk81 authored Sep 19, 2013 35 zRow.push(zScores(roundTo(2, 36 (floorTo(0, ZSCORE) + i / 10 + j / 100) * 100))); 9fdecff beneater authored Apr 16, 2012 37 } 38 zGrid.push(zRow); 39 } 40 return zGrid; 41 })() 42 43 ZGRID[ROW_INDEX][COL_INDEX] 44 "z" 45
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47 The scores on a statewide course(1) exam were normally distributed with 48 \mu = MEAN and \sigma = STDDEV. 08a4096 Tweak question wording petercollingridge authored May 7, 2014 49
person(1) scored GRADE on the exam. 9fdecff beneater authored Apr 16, 2012 50
08a4096 Tweak question wording petercollingridge authored May 7, 2014 51

35e1ca9 Rearrange answer area content within some exercises xymostech authored Nov 13, 2014 52 person(1)'s exam grade was higher than what percentage of test-takers?

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114a43c lint ariabuckles authored Nov 20, 2014 54

Use the cumulative z-table provided below.

08a4096 Tweak question wording petercollingridge authored May 7, 2014 55
d5bdea4 mauk81 authored Sep 19, 2013 56 HEADERlocaleToFixed(column, 2).substr(1) 9fdecff beneater authored Apr 16, 2012 57
08a4096 Tweak question wording petercollingridge authored May 7, 2014 58
d5bdea4 mauk81 authored Sep 19, 2013 59 rowlocaleToFixed(zgrid, 4) 9fdecff beneater authored Apr 16, 2012 60
9d0ccf7 Move z-table styles to external file and allow for answers 0.0001 out petercollingridge authored Jun 3, 2014 61
e27b12e New exercise: Z-scores 2: Reading a z-table smenks13 authored Mar 6, 2012 64 9fdecff beneater authored Apr 16, 2012 65
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67 A cumulative z-table shows the probability that a standard normal variable will be 68 less than a certain value (z). 69

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71 In order to use the z-table, we first need to determine the 72 z-score of person( 1 )'s exam grade. 73

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9de9147 Add in a tool for automatically fixing some i18n issues in exercises.… jeresig authored Apr 5, 2013 75

76 Recall that we can calculate his z-score by subtracting the 77 mean (\mu) from his 08a4096 Tweak question wording petercollingridge authored May 7, 2014 78 grade and then dividing by the standard deviation 9de9147 Add in a tool for automatically fixing some i18n issues in exercises.… jeresig authored Apr 6, 2013 79 (\sigma). 80

81 Recall that we can calculate her z-score by subtracting the 82 mean (\mu) from her 08a4096 Tweak question wording petercollingridge authored May 7, 2014 83 grade and then dividing by the standard deviation 9fdecff beneater authored Apr 16, 2012 84 (\sigma). 85

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87 88 \large{\quad z \quad = \quad 08a4096 Tweak question wording petercollingridge authored May 7, 2014 89 \dfrac{x - \pink{\mu}}{\purple{\sigma}} 90 \quad = \quad \dfrac{GRADE - \pink{MEAN}}{\purple{STDDEV}} d5bdea4 mauk81 authored Sep 19, 2013 91 \quad = \quad localeToFixed(ZSCORE, 2)} 9fdecff beneater authored Apr 16, 2012 92 93

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d5bdea4 mauk81 authored Sep 19, 2013 97 Look up localeToFixed(ZSCORE, 2) on the z-table. This value, 98 localeToFixed(ANSWER, 4), represents 9fdecff beneater authored Apr 16, 2012 99 the portion of the population that scored lower than 100 GRADE on the exam. 101

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103 var nth = ":nth-child(" + (COL_INDEX + 2) + ")"; 104 $(".fake_row").eq(ROW_INDEX).find("span").css("background", ORANGE); 105$(".fake_row span" + nth).css("background", ORANGE); 106 $(".fake_header span" + nth).css("background", ORANGE); 107$(".fake_row").eq(ROW_INDEX).find("span" + nth).css("background", BLUE); 108
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111 person( 1 ) scored higher than d5bdea4 mauk81 authored Sep 19, 2013 112 localeToFixed(ANSWER * 100, 2)\% of the 9fdecff beneater authored Apr 16, 2012 113 test-takers on the course( 1 ) exam. 114

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ced362c Run the exercise cleaner. jeresig authored Apr 23, 2013 119 120
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