1. Name: Date: Block:
Lab 2.7: The Titanic Shuffle
Notes:
In the lastlab,we learnedthatbyusinga do-loopandthe resample function,we couldsimulate
shufflingourdatamanytimes. Thishelpsusdeterminehow likelyitisthata difference betweengroups
isdue to chance.
Data scientistsusuallyconsideranyz-score largerthan3 or smallerthan -3 to be extreme.
Andby extreme we meanthattheyoccurso rarelyby chance alone that we start to believe that
somethingbesideschance alone is causingthe z-scorestobe solarge.
1. Lookat the boxplotof farespaidseparatedbywhetherthe passengersurvivedornot. Do you
believericherpassengerswere more likelytosurvive?Why? Refertothe quartilestosupportyour
claim.
2. Calculate howmuchmore the typical survivorpaidversusthe typical non-survivorinourdata. Copy
the resulthere:
3. What wasthe typical fare paidbysurvivors?Non-survivers?How muchmore didthe typical survivor
pay?Write the code youusedto findthese answers.
4. Basedon the boxplots,whywouldusingthe medianbe abettermeasure of typical thanthe mean?
5. Use a do-loopandthe resample functiontoshuffle the passenger'ssurvival status300 timesand
compute eachgroup's medianfare paid.Save yourshuffleddataasa new objectcalledshfl_med. Paste
your code here:
(hint:You can look in lab 2.6 for help with constructing thecode.)
6. Type inthe commandhead(shfl_med) andpaste the resulthere:
7. Use the transformfunctiontoadd a variable calledDiff tothe shuffledmediansyoujustcalculated.
Save these valuesasa newobjectcalledshfl_diff . Paste yourcode here:

2. (hint:Youcan lookinlab2.6 for helpwithconstructingthe code.)
8. Type inthe commandhead(shfl_diff)andpaste yourresulthere:
9. Create a plotof the mediandifferencesinthe fare paidforyourrandomizedsurvivorsandnon-
survivors. Copyandpaste your plothere:
10. What was the actual difference inthe medianfare paidbysurvivorsandnon-survivors inthe data?
Basedon yourplot,do youthinkthisdifference isbig?Why?
11. Compute the meanand standarddeviationof your300 randomizeddifferences.
What code didyou use to findthe mean?
Paste the resulthere:
What code didyou use to findthe standarddeviation?
Paste the resulthere:
12. Convertthe actual difference youcomputedtoaz-score usingthe meanandstandard deviations
youjust computed.Write downthe formulayouusedandthe z-score you got.
13. How manystandarddeviationsawayfromthe meanisthe actual mediandifference infarespaidby
survivorsandnon-survivors?
14. Use the subsetandnrow functionstocompute the estimatedprobabilitiesof az-score beinglarger
than 3, smallerthan -3, andlarger than3 OR smallerthan-3. Assignthissubsetthe name
zscore_probability.
What code didyou use?
Paste yourresulthere:

3. Redo your simulationand the analysis,BUT thistime use the meanfare paid insteadof the median
fare paid.
15. Use a do-loopandthe resample functiontoshuffle the passenger'ssurvival status300 timesand
compute eachgroup's meanfare paid.Save yourshuffleddata asa new objectcalledshfl_mean. Paste
your code here:
16. Type in the commandhead(shfl_mean)andpaste the resulthere:
17. Use the transformfunctiontoadda variable calledDifftothe shuffledmeansyoujustcalculated.
Save these valuesasa newobjectcalledshfl_diff2. Paste your code here:
18. Type in the commandhead(shfl_diff2) andpaste yourresulthere:
19. Create a plotof the meandifferencesinthe fare paidforyourrandomizedsurvivorsandnon-
survivors. Copyandpaste your plothere:
20. What was the actual difference inthe meanfare paidbysurvivorsandnon-survivorsinthe data?
Basedon yourplot,do youthinkthisdifference isbig?Why?
21. Compute the standarddeviationof your300 randomizeddifferences.
What code didyou use to findthe standarddeviation?
Paste the resulthere:
22. Convertthe actual difference youcomputedtoaz-score usingthe real meanand standard
deviation.Write downthe formulayouusedandthe z-score yougot.
23. How manystandarddeviationsawayfromthe meanisthe actual mediandifference infarespaidby
survivorsandnon-survivors?
24. Doesyour conclusion change dependingonthe methodyouuse todescribe the typical fare paidby
survivorsandnon-survivors?Explain.
25. If a journalistwalkeduptoyou rightnow and askedif the amountof fare paidfor a Titanicticket
had an effectona person'sprobabilityof surviving,whatwouldyousay?How wouldyoujustifyyour
answer?