Statistical Degrees of Freedom Question
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 This topic has 5 replies, 5 voices, and was last updated 1 year, 6 months ago by Fausto Galetto.

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January 21, 2020 at 9:34 pm #245666
ginloenParticipant@ginloen Include @ginloen in your post and this person will
be notified via email.Hi all,
Sorry to bother you guys. I have tried attempting to solve this question for some time now. I just cannot figure out what the question is asking. Would someone please enlightened me? Thanks in advance!
Sally and Sara sell flower pots at their garage sale. Sally motivates Sara mentioning that they will sell a minimum of 15 pots per day if the outside temperature exceeds 60o F.
From a sample, whose population is assumed to follow a Normal Distribution, taken for 30 days at 60 degrees or more an average of 13.6 pots per day were sold with a Standard Deviation of 0.7 pots.
The statistical Degrees of Freedom for this example are?
Response:
a) 29 (answer)
b) 1
c) 31
d) 30
e) 20January 21, 2020 at 9:37 pm #245668
Katie BarryMember@KatieBarry Include @KatieBarry in your post and this person will
be notified via email.@ginloen You’ve said you’ve tried to solve this yourself. How? What do you think you’re doing right or wrong? The more details you provide, the more likely you are to get a response. The iSixSigma audience is helpful, but they like to see that someone is putting forth a goodfaith effort.
0January 21, 2020 at 10:00 pm #245669
ginloenParticipant@ginloen Include @ginloen in your post and this person will
be notified via email.Hi Katie,
Thank you for replying so quickly.
I am trying to find degrees of freedom, the formula that I know
df = n− 1
I have x̄ = 13.6, s = 0.7, µ= 15. I am trying to get n so I tried using the formula
x̄ ± Z * (sample s.d./√n) = µ (I just assume Z = 1.96 at 95% C.I)
Solving for n, i got 0.9 which does not make any sense.
0January 22, 2020 at 4:26 am #245674Hello
Degrees of Freedom is based on the number of units under studied to arrive at the statistics like mean and standard deviation. Since we are studying 30 units, degrees of freedom in this case is (301)=29 where n = 30 in this example.
1January 23, 2020 at 6:31 am #245691
Sergey GlukhovParticipant@[email protected] Include @[email protected] in your post and this person will
be notified via email.In statistics there is a strange concept of degrees freedom which means that when using any statistical formula that divides any expression by the number of data we have to adjust divider to the number of degrees of freedom (df).
df is calculated by formula:
df = number of independent data (n or 30 days temperature in your example) – number of calculated vaiables in formula (1 for mean which is calculated on the 30 days data set).
If you had more calculated variables in the formula then the degrees of freedom would be less accordingly.
0March 4, 2020 at 11:34 am #246493
Fausto GalettoParticipant@fausto.galetto Include @fausto.galetto in your post and this person will
be notified via email.YOU SAY:
I am trying to find degrees of freedom, the formula that I know
df = n− 1
THIS FORMULA is NONSENSE in your case
From a sample, whose population is assumed to follow a Normal Distribution, taken for 30 days at 60 degrees or more an average of 13.6 pots per day were sold with a Standard Deviation of 0.7 pots.
HOW MANY DAYS was long your time observation? Let’s say 80…
SO you have 20 days with temperature less that 60 degrees!!!!!!!!
IF YOU STUDY THEORY you will find the df
0 
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