## bobobox one year ago I need help with a couple question on two way frequency tables

1. bobobox

ONce someone asks I will post a screencap

2. jim_thompson5910

3. bobobox

okay

4. bobobox

@jim_thompson5910 heres the question

5. jim_thompson5910

ok one sec

6. bobobox

here is the options

7. jim_thompson5910

what are your thoughts on this?

8. bobobox

Im looking for a working pen one moment

9. bobobox

okay let me write down the problem

10. jim_thompson5910

ok

11. bobobox

sorry i just found my paper

12. jim_thompson5910

thats fine

13. bobobox

Okay so I think I need to look at the comlums and ad the two row in each colum together to see what number I must divde by?

14. jim_thompson5910

why divide?

15. bobobox

Well I would say so I have numbers to add together for the bottom row of my colum

16. jim_thompson5910

all they want you to do is rearrange the given info into a table then add up the rows to get the row totals afterwards, add up the columns to get the column totals no division is done at all

17. bobobox

really? Im having trouble so I watched a kahn academy video and they said to divide! Now I am really confused

18. jim_thompson5910

you divide if they wanted RELATIVE frequencies

19. bobobox

20. jim_thompson5910

normal frequencies are counts (whole numbers) relative frequencies are percentages, fractions or decimal form

21. bobobox

okay what about two way frequecies

22. jim_thompson5910

how many men like playing sports

23. bobobox

11

24. jim_thompson5910

so "11" goes in the "Men" row and "Playing sports" column

25. jim_thompson5910

the other values are done in a similar way

26. bobobox

really thats it?

27. jim_thompson5910

yep

28. jim_thompson5910

again they just want normal frequencies

29. bobobox

30. jim_thompson5910

correct

31. jim_thompson5910

notice how they have "row totals" and "column totals" do you see how those numbers were formed?

32. bobobox

Okay can you double check my answer for the next?

33. jim_thompson5910

sure

34. bobobox

heres the question

35. bobobox

I picked a

36. jim_thompson5910

now notice how the keyword "relative frequency" comes up

37. jim_thompson5910

it's not a simple count anymore

38. jim_thompson5910

that "relative" changes everything

39. bobobox

Oh do I divide with this one?

40. jim_thompson5910

yes division will play a part now

41. bobobox

okay let me take a crack at it. See I think I watched a video on realative

42. jim_thompson5910

yeah it sounds like it too

43. bobobox

I think its b!!!!!

44. jim_thompson5910

why B?

45. bobobox

because I was dividing the number in the colum/row by the colum total In the chart I made with they numbers I was given and got the same answers in the chart B!

46. jim_thompson5910

Notice there are 26 people who are in high school and like action this is out of 128 people total (see table in choice A or you can add up all the numbers)

47. jim_thompson5910

so the relative frequency of those who are in high school and love action movies is 26/128 = 0.203125 that rounds to 0.20

48. jim_thompson5910

in a normal frequency table, "26" goes in the "high school" and "action" column in a relative frequency table, "0.20" goes in the "high school" and "action" column (since 26/128 is roughly 0.20)

49. bobobox

one sec

50. jim_thompson5910

and like before, the other relative frequencies are calculated in a similar way

51. bobobox

so you divide by 128? I divded by 46

52. jim_thompson5910

why 46?

53. bobobox

it was that comlum total and I listened incorrectly

54. bobobox

oh im dividing by 128 and i get it now its D

55. jim_thompson5910

well when they mean "relative" without specifying anything further, they mean relative to the entire group so 26/128 = 0.20 roughly means that approximately 20% of the entire group is in high school and likes action movies if it said "relative to action movies" then it would work. Or if it said "of those who like action movies, what is the relative frequency of those in high school?" then it would work

56. jim_thompson5910

yeah it's D

57. bobobox

58. bobobox

59. bobobox

question

60. bobobox

Can you teach me what this means?

61. jim_thompson5910

let me look it over

62. bobobox

I want to say B for some reason because they didn't say relative

63. bobobox

@jim_thompson5910

64. jim_thompson5910

I'm still thinking on this one

65. bobobox

66. jim_thompson5910

ok hopefully I have the right interpretation

67. bobobox

okay

68. jim_thompson5910

they ask "Which of the following is a two-way conditional frequency table for gender?" so in a sense, they want to compare the results between genders (to see which percent like Aspen for instance)

69. bobobox

okay...

70. jim_thompson5910

it might help to take that original table and convert it to a frequency table (not a relative frequency table)

71. jim_thompson5910

let's say there are 100 people how many of those 100 people are male and like aspen?

72. bobobox

22%

73. jim_thompson5910

22% of 100 = ???

74. bobobox

22

75. jim_thompson5910

how many females like aspen?

76. bobobox

16

77. jim_thompson5910

so 22+16 = 38 people like aspen

78. bobobox

okay aand 63 people like nyc

79. jim_thompson5910

22 males like aspen 38 people total like aspen if you just focus on aspen (ignore the other location), what is the percentage of males who like aspen?

80. bobobox

44% of males enjoy aspen

81. jim_thompson5910

ignore the other location

82. bobobox

okay,

83. bobobox

so is it still 22 or is it 44 i multiplied by 2 because it would make sense if there was one hundred men 44 enjoy aspen

84. jim_thompson5910

22 males like aspen 38 people total like aspen 22/38 = ??

85. bobobox

0.57

86. jim_thompson5910

22/38 = 0.57894736842106 which rounds to 0.58

87. jim_thompson5910

so 58% of the people who like aspen are male

88. bobobox

okay

89. jim_thompson5910

fill in the blank ____ percent of the people who like aspen are female

90. bobobox

42%

91. jim_thompson5910

yes

92. bobobox

is it A?!?!?!?! eeeeeeeeeee

93. jim_thompson5910

yeah

94. jim_thompson5910

that's assuming my interpretation was correct

95. bobobox

okay next one lol so srry but I am learning a ton

96. bobobox

97. bobobox

that was the question and options

98. jim_thompson5910

99. bobobox

no clue I need to learn that fancy vocabulary

100. jim_thompson5910

so all of the terms are unfamiliar?

101. bobobox

yes

102. bobobox

if you tell me what each word means I might be able to make an educated guess

103. jim_thompson5910

Ok let's make up an example

104. jim_thompson5910

Let's say we have males and females and let's say we want to know if they like coke or pepsi I'm just going to randomly make up data Males: 12 like coke, 10 like pepsi Females 8 like coke, 13 like pepsi

105. bobobox

okay I get that so far

106. jim_thompson5910

|dw:1435452321297:dw|

107. jim_thompson5910

go ahead and fill out the table (click the pencil to draw on my drawing)

108. bobobox

|dw:1435452206385:dw|

109. jim_thompson5910

the 86 is incorrect, but everything else looks good

110. bobobox

|dw:1435452344153:dw|

111. jim_thompson5910

better

112. jim_thompson5910

you only add either the row totals OR the column totals (pick one)

113. jim_thompson5910

the numbers I'm circling are called `joint frequencies` |dw:1435452635430:dw|

114. bobobox

okay

115. jim_thompson5910

they are frequencies (whole numbers, counts of something) the "joint" means the frequencies represent 2 different things. For instance, the 12 represents "male" and "coke" at the same time think of "joint" as in "joint bank account" (2 or more people own/access it) or as in "joints in your body" (connecting 2 bones together)

116. bobobox

okay joints=2+

117. jim_thompson5910

now if you divide every value by the total number of people (43), you will get this |dw:1435452804260:dw|

118. bobobox

okay i see how you got that

119. jim_thompson5910

these circled values are called `joint relative frequencies` |dw:1435453025373:dw| they are basically `joint frequencies` but divided by the total (in this case 43)

120. jim_thompson5910

for example, 0.28 is a `joint relative frequency` it means "28% of the entire group is male and likes coke"

121. bobobox

okay

122. jim_thompson5910

notice how 43*.28 = 12.04 which is pretty close to the original 12

123. bobobox

yeah you just rounded

124. jim_thompson5910

ok more terms

125. bobobox

okay throw them at me

126. jim_thompson5910

these are marginal frequencies |dw:1435453144401:dw|

127. jim_thompson5910

they are in the margins (off to the side, think margins on a paper) and they are frequencies (whole number counts)

128. bobobox

wait does frequency=whole number counts=?

129. jim_thompson5910

frequency is just a fancy way of saying how many times it happens

130. jim_thompson5910

so yeah it's a count of something

131. bobobox

okay sorry continue

132. jim_thompson5910

marginal relative frequencies are basically the same as joint relative frequencies just now you focus on the margins |dw:1435453312087:dw|

133. bobobox

okay @jim_thompson5910 sorry if I am a little spotty dont worry I am still here

134. jim_thompson5910

its fine

135. bobobox

okay

136. bobobox

@jim_thompson5910

137. jim_thompson5910

yes?

138. bobobox

so I m thinking of the answer to the actual question now

139. jim_thompson5910

what are you thinking so far

140. bobobox

wait relative=?

141. jim_thompson5910

it means a piece of, or percentage of

142. jim_thompson5910

it's like a proportion

143. bobobox

okay I am making an educated guess here.. is it B? since its a decimal

144. jim_thompson5910

and why is it not D?

145. bobobox

hmmm... I think it's B becuase it represents two things, female students and dancing, but then again it could be marginal

146. jim_thompson5910

is that value in the margins?

147. bobobox

no

148. bobobox

the colum next to it is the total value of the margin

149. jim_thompson5910

so it can't be a marginal relative frequency

150. bobobox

okay so my educated guess was right!

151. jim_thompson5910

yes

152. bobobox

here is the next one you are really helping me

153. bobobox

@jim_thompson5910

154. jim_thompson5910

post in a new question. I'm lagging really badly since there's so much on this post