vending machine adventures by: pat casey, dan cardamone, heejun yang
TRANSCRIPT
Vending Machine Adventures
By: Pat Casey, Dan Cardamone, Heejun Yang
Description
• We basically studied the vending machine food habits of the typical high school teenager– First, we did a test on vending machine drinks and
their association to gender. Also, we found the mean amount spent on these drinks compared through gender.
– Second, we did a test upon food/snacks of vending machines and the difference of the means of each gender.
Procedure
• We sat through all the lunches and surveyed the attendance of both food and drink vending machines. We surveyed every third person for a systematic sampling.– For drinks, we checked a chi-square association,
along with 2 sample t-test to find the mean dollar amount spent at the drink vending machine
– For food, we used, again, a 2 sample t-test to find the mean dollar amount spent at the food vending machine
Vending Machine DrinksSpecialty Water (Vitamin Water, Carbonated Water)
Iced Tea Gatorade/Propel
Water Other (Soda, Yoo Hoo)
Male 12 6 7 5 7
Female 8 9 8 9 6
Vending Machine Drinks
Vending Machine Drinks
32%
16%
19%
14%
19%
20%
23%
20%
23%
15%
Vending Machine Drinks
• association– Ho: There is no association between gender and
type of drink preferred.– Ha: There is an association between gender and
type of drink preferred.
2
Assumptions STATE CHECK2 independent SRS Systematic
Sample size large All expected cell counts 5 enough so all expected cellcounts 5
Vending Machine Drinks
P ( 2 2.5734 df 4) .6315
df= (2-1) * (5-1) = 4
2 (obs exp)2
exp
(12 9.6104)2
9.6104
(6 7.2078)2
7.2078 ...2.5734
Vending Machine Drinks
ConclusionWe fail to reject Ho because the p-value of .6315 is greater than = .05.We have sufficient evidence that there is no association between gender and type of drink preferred. This concludes that type of drink does not change as the gender changes.
Vending Machine Drinks
• 2 Samp T-Test• Ho: • Ha:
M F
M F
Assumptions STATE CHECK2 independent SRS Systematic
2 normal populations NM=37 or NF=40NM
NF
30
30
Vending Machine Drinks
We fail to reject Ho because the p-value of .2276 is greater than =.05. We have sufficient evidence that the difference of the mean amount of money spent at the drink vending machines for males is equal to that of females. Thus, both females and males spend the same amount of money on drinks at the vending machines
t (XM XF )
SM2
nMSF
2
nF
1.217
P(t 1.217 df 72.62) .2276
Vending Machine Drinks
XM XF t*SM
2
nMSF
2
nF( .0379,.1585)
We are 95% confident that the difference between the mean amount of dollars spent at the drink vending machines between males and females is between -.0379 and .1585. With this 0 is included in the interval meaning that there is no difference between the male and female mean amount of dollars spent at the drink vending machines. It can be concluded that there is no difference because 0 is within the interval.
Vending Machine Foods
$.90 Spent $1.00 Spent $1.80 Spent $1.90 Spent $2.00 Spent
Male 15 12 1 2 1
Female 18 7 2 1 2
Vending Machine Foods
Vending Machine Foods
48%39%3%6%3%
60%23%7%3%7%
Vending Machine Foods
• 2 Samp T-Test• Ho: • Ha:
M F
M F
Assumptions STATE CHECK2 independent SRS Systematic2 normal populations NM=31 or NF=30NM
NF
30
30
Vending Machine Foods
t (XM XF )
SM2
nMSF
2
nF
.2467
P(t .2467 df 57.634) .806
We fail to reject Ho because the p-value of .806 is greater than =.05. We have sufficient evidence that the difference of the mean amount of money spent at the food vending machines for males is equal to that of females. Thus, both females and males spend the same amount of money at a food vending machine.
Vending Machine Foods
XM XF t*SM
2
nMSF
2
nF( .2029,.15839)
We are 95% confident that the difference between the mean amount of dollars spent at the food vending machines between males and females is between -.2029 and .15839. With this 0 is included in the interval meaning that there is no difference between the male and female mean amount of dollars spent at the food vending machines. It can be concluded that there is no difference because 0 is within the interval.
Conclusions
• For drink vending machines we found that both males and females seemed to spend the same amount of money on the drink machine and both gender and type of drink preferred are not associated.
• For food vending machines, males and females spend the same amount of money at a food vending machine.
Conclusions
• We found that overall both males and females seem to have the same preference and same spending habits for vending machines at lunchtime in the cafeteria.
• For the male population…– Buy more of the specialty water• Like sweetness, but try to be healthy
– Buy mostly $.90 and $1.00 products• Don’t have a lot of money
Conclusions
• For the female population…– Buy more of water
• Try to be healthy– More of uniform preference– Buy more $.90 and $1.00 products
• Similarities between genders more related to culture and generation preferences
Application
• It was harder than thought to collect the data– Not as many people buy from the vending
machines• Healthy effort
• We were surprised somewhat– Males thought to choose more of vending
machine sweets and gatorade (sports-related)– Females thought to choose the most water and
specialty water, but more uniform
Bias
• Tough economic times=less money• Not SRS– Systematic
• Struggled to get good sample size• Absentees from– Early release, etc.
• Not a lot of choices of drinks/foods