CB South Student Lunches

By: Lindsay, Danielle, Brit

About Student Lunches• CB South offers a variety of food options for students to

choose from, in addition to meal deals at lower costs.• Food includes nachos, salads, wraps, sandwiches,

French fries, and a special cooked meal everyday.• The food available is clearly more towards the

unhealthy side, despite government and school attempts at tackling childhood obesity.

• This inspired us to observe the eating habits of students and conclude about the overall preference of foods at South.

Focused on…

• Differences in CB South student lunches– Types of junk food

– Proportion of chips

– Bought or brought lunch

– Gender

Sample MenuFairfax County High School

http://www.fcps.edu/fs/food/food_at_school/menus/HS-May10.pdf

The Food Pyramid

Food Health Facts• Study finds pupils eating excessive amounts of salt and fat – even though

school meals are getting healthier• "Parents will be shocked to realize that their teenagers could be getting

more than a day's dose of salt before they even get home from school":Rob Rees

• Children who eat high-salt diets have higher blood pressure and greater risk of a heart attack or stroke

• Forty percent of moms send money with kids to buy lunches• Over 70% pack sandwiches and 40% pack fruit.• 42% of 11-12 year olds want to pack chips and 39% of younger children

like juice boxes.• 40% of children say favorite food would be pizza and food suited for

dipping

Taking a Sample/Observational Study

• All four lunches • Observed on June 4, 2010• Randomly select 5 tables per lunch• Observe 6 student’s lunches per table– (30 students per lunch, n=120 students)

• Record all items we want to focus on as well as type of drink and what type of junk food they eat after school, if they do eat after school

Chi-Square Assumptions#1

State1. 2 independent SRS

2. Sample size large enough so that all expected counts are greater than or equal to 5

Check1. Assumed

2.

χ² Test #1Gender vs. Junk Food Eaten

Ho: There is no association between gender and what junk food is eaten in lunches.

Ha: There is an association between gender and what junk food is eaten in lunches.

Observed

Male FemaleFruit 8 20Chips 19 12Pretzels 6 11Candy 11 9Other 15 9

Expected Male FemaleFruit 13.76 14.23Chips 15.24 15.76Pretzels 8.36 8.64Candy 9.83 10.17Other 11.8 12.2

χ² Test #1Gender vs. Junk Food Eaten

0428.04|86.92 dfP 86 . 9 ...

24 . 15) 24 . 15 19 (

76 . 13) 76 . 13 8( ) (

2 2 22

ExpExp Obs

We reject Ho because the p-values is less than α=0.05We have sufficient evidence that there is an association between gender and what junk food is eaten.

Chi-Square Test for Association#1

Fruit Chips Pretzels Candy Other0

5

10

15

20

25

MaleFemale

Exploratory Data Analysis#1

• The male distribution is roughly symmetric indicating no clear preference. However, males prefer chips more than females.

• This is probably because males go for snacks with more carbs to keep up with their activeness, which salty snacks usually contain, and also the fact that males tend to be not as concerned with calories as females.

• The female distribution is more right skewed, showing that females prefer healthy snacks like fruit more than unhealthy snacks.

• Our findings prove that for the population of CB South, there is an association between gender and junk food eaten. Females are more aware of what they’re eating, whereas men tend to eat whatever they want.

1 proportion z-testPrefer Chips

Ho: p= 0.42Ha: p> 0.42

Test Stat:

P(z > 2.5154)= 0.0059

We reject Ho because the p-value is less than α=0.05.We have sufficient evidence that the percentage of students

that prefer chips is greater than 42%.

5154.2

120)42.01(42.0

42.05333.0

z

1 proportion Assumptions

State

1. SRS

2.

3. population ≥ 10n

Check1. Assumed

2.

3. Population ≥ 10(120)

)5333.01(120)5333.0(120

10

10

)ˆ1(ˆ

pnpn

1-Proportion z-test

Prefers Chips Prefers Other0

5

10

15

20

25

30

35

40

MaleFemale

Exploratory Data Analysis #2• Based on our sample data, males seem to prefer chips and

females seem to prefer other snack when they go home after school.

• These other snacks include fruit, cookies, crackers, candy, chocolate, ice cream.

• Females tend to prefer sweet snacks due to different hormones.

• Overall, the male population of CB South prefers chips more than the female population at school.

• Based on our findings, the percentage of students at CB South who prefer chips is greater than our researched claim of 42%.

1 proportion z-testBought Lunch

Ho: p= 0.50Ha: p> 0.50

Test Stat:

P(z < -1.278)= 0.4417 nppppz)1(

ˆ

We fail to reject Ho because the p-value is greater than α=.05.We have sufficient evidence that the proportion of students that bought lunch in all 4 lunches is equal to 0.50.

278.1

120)50.01(50.0

50.03533.0

z

1 proportion Assumptions #3

State

1. SRS

2.

3. population ≥ 10n

Check1. Assumed

2.

3. Population ≥ 10(120)

)ˆ1(ˆ

pnpn

10 )50.1(120

)50(.120

10

1 Proportion z-test

Buy Bring Both0

5

10

15

20

25

30

35

Male

Female

Exploratory Data Analysis #3

• Males are more likely to buy lunch. This is most likely because cafeteria lunches offer more and men usually have bigger appetites. They are also more likely to both buy and bring lunch everyday.

• Females seem to bring lunches from home more often because they seem to eat lighter and pack their own lunches more often.

Bias/Error

• Time of lunch• What food is served in the cafeteria (for those

who bought lunch)• Day of week• Food Allergies• Who packs the lunch (parent or student)• Whether or not student ate breakfast• Mood of student during time of observation

Personal Opinions

• Before our observations, we thought more students would prefer chips than the claim and that more than half would buy lunches.

• We believed females would say they snacked healthier (fruit) and were more likely to pack a lunch.

• We thought males would more likely buy lunch and prefer chips to other snacks.

• Taking a sample was easy• Difficult to know if people were telling the truth or not

Conclusions• We believe our data is plausible.• Students seem to prefer chips as a whole (both male and

female) than they do other junk foods. • Also, more students seem to bring lunches from home than

buy them since it’s cheaper and easier. • The proportion of students that prefer chips is most likely

greater than 42% (our original claim) especially since we had more males in our sample and more males said that they preferred chips.

• It’s likely that there’s an association between food and gender due to hormones and common preferences.