## help123please. 2 years ago Display the data in the chart attached below by making a box and whisker plot. Explain how you made it.

@rajathsbhat

3. rajathsbhat

statistics....we meet again.

LOL. Are you not so good with them?

5. rajathsbhat

not so good is an overstatement.

6. rajathsbhat

*understatement. I suck at it.

Oh, ok. thats fine, no worries. Ill go beg someone else. :D

Thanks for looking,tho.

9. pooja195
10. pooja195

see if this helps :)

Hmm... could you explain it step by step?

12. pooja195

hold on

ok. ty:)

14. pooja195

you find the median of your data.

15. pooja195

have u done that

one second - let me do it.

Median: 68

18. pooja195

goodTo divide the data into quarters, you then find the medians of these two halves. Note: If you have an even number of values, so the first median was the average of the two middle values, then you include the middle values in your sub-median computations. If you have an odd number of values, so the first median was an actual data point, then you do not include that value in your sub-median computations. That is, to find the sub-medians, you're only looking at the values that haven't yet been used

hmmm.

let me read all that.

21. pooja195

srry

why are you sorry?

23. pooja195

too much to read :)

indeed. lol.

could u simplify it?

26. pooja195

divide the data into quarters, you then find the medians of these two halves.

hmmm...could u show me the steps by using the DRAW button?

29. pooja195

Hmm. Okay. Thanks.

Lets see.....

@eigenschmeigen

33. pooja195

@jim_thompson5910

34. jim_thompson5910

I have to make a box and whisker plot for the data shown at http://assets.openstudy.com/updates/attachments/5148e6dee4b05e69bfab6578-help123please.-1363732200597-screenshot20130319at5.28.53pm.png

I also would like to know how to make box and whisker plots by myself.

37. jim_thompson5910

Find the median first Then split the data into two groups (the median is the cut off point) and find the median of each group. The first quartile is the median of the lower half, the third quartile is the median of the upper half

the median is 68.

ok.....hmmm...

oohhhh divide it into 2?

8/2=4

so 4 sets of data in the lower quartile and 4 in the upper?

43. jim_thompson5910

yes the median is 68

Okay.

show me step by step how to make it using the DRAW button please?

46. jim_thompson5910

so the sorted number set 61, 64, 65, 68, 68, 70, 71, 73 turns into 61, 64, 65, 68 | 68, 70, 71, 73 when you split the data in half along the median

Uh-huh, I see.

48. jim_thompson5910

the median of 61, 64, 65, 68 is 64.5, so Q1 = 64.5

Okay.

50. jim_thompson5910

what's Q3?

Let me see. One second.

52. jim_thompson5910

ok

70.5

54. jim_thompson5910

good

55. jim_thompson5910

i don't know how to get that...

57. jim_thompson5910

IQR = Q3 - Q1

58. jim_thompson5910

it's basically the distance from each endpoint of the box

Oh,ok.

70.5-64.5?

61. jim_thompson5910

yep

thats 6.

63. jim_thompson5910

now find the min and max

The min and max?

65. jim_thompson5910

yes, the smallest and largest data values

oh... U mean min = 61 max = 73

67. jim_thompson5910

good, now determine if the min is an outlier or not

68. jim_thompson5910

you do this by seeing if the min is above median - 1.5*IQR

Why 1.5?

70. jim_thompson5910

just a number that some statistician a long time ago determined was the best number to see if outliers exist on a box and whisker plot

71. jim_thompson5910

I think it was Tukey

Oh.

73. jim_thompson5910

I'm not sure how or why he got 1.5, but it works

74. jim_thompson5910

and people agree on it

and the iqr is?

76. jim_thompson5910

you just found it

o sorry....6

78. jim_thompson5910

yep

1.5 x 6 = 9

80. jim_thompson5910

subtract that from the median 68

Hmm. Ok. WOW, lots of steps :/ LOL.

82. jim_thompson5910

it's not so bad once you get used to them

56.

84. jim_thompson5910

no

85. jim_thompson5910

68 - 9 is not 56

86. jim_thompson5910

it's 59

o right sorry.

88. jim_thompson5910

so that's your lowest threshold

i punched the wrong numbers into the calculator.

90. jim_thompson5910

basically that's the smallest the min can be

sorry bout that.

92. jim_thompson5910

any smaller than 59, and the min is an outlier

Ah,ok.

94. jim_thompson5910

so we do NOT have an outlier for the min because the min (which is 61) is greater than the threshold of 59

95. jim_thompson5910

now compute median + 1.5*IQR

Mhmm. Okay. One second - will log off for like 2 mins,k?

ill brb

98. jim_thompson5910

ok

im back

100. jim_thompson5910

ok

101. jim_thompson5910

did you find median + 1.5*IQR

lets see. the median was?

103. jim_thompson5910

68

68. so 68-9... 59?

105. jim_thompson5910

you already did that one

its not the answer?

107. jim_thompson5910

no I wanted you to find median + 1.5*IQR

Oh...Ok.

68+1.5*9

110. jim_thompson5910

yeah but the IQR is 6, not 9

right,sorry

77

113. jim_thompson5910

good, is the max smaller or larger than 77?

The max is 73, so its larger.

115. jim_thompson5910

you mean, the max is smaller than 77?

Right.

117. jim_thompson5910

so does that make the max an outlier?

no.

wait..

120. jim_thompson5910

so there are no outliers

121. jim_thompson5910

you're correct

nvm.

oh,okay.

124. jim_thompson5910

so you have enough info to plot the box and whisker plot

Alright,thanks!

126. jim_thompson5910

The basic format (the chances of your box and whisker plot looking exactly like this are very slim) is this |dw:1363736245038:dw|

Yes.

128. jim_thompson5910

|dw:1363736267701:dw|

129. jim_thompson5910

this is if you don't have any outliers

Okay. I think I understand a bit better- thanks!

131. jim_thompson5910

yw