Re: P Values
The original question was about p-value (lower case), not P-value (upper case). There's a difference.
The original question was about p-value (lower case), not P-value (upper case). There's a difference.
P Values - In understandable terms what does the P Value represent?
- Thread starter cpine
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Re: P Values
From Minitab:
"p-values are often used in hypothesis tests where you either accept or reject a null hypothesis. The p-value represents the probability of making a Type I error, or rejecting the null hypothesis when it is true. The smaller the p-value, the smaller is the probability that you would be making a mistake by rejecting the null hypothesis. A cutoff value often used is 0.05, that is, reject the null hypothesis when the p-value is less than 0.05."
To me, p-value is the same as <alpha> in hypothesis testing. It is also the level of significance or Type I error.
Wes R.
From Minitab:
"p-values are often used in hypothesis tests where you either accept or reject a null hypothesis. The p-value represents the probability of making a Type I error, or rejecting the null hypothesis when it is true. The smaller the p-value, the smaller is the probability that you would be making a mistake by rejecting the null hypothesis. A cutoff value often used is 0.05, that is, reject the null hypothesis when the p-value is less than 0.05."
To me, p-value is the same as <alpha> in hypothesis testing. It is also the level of significance or Type I error.
Wes R.
B
bruceliu222
In minitab six-pack, P<0.05 normally indicates the non-normal process if the samples are 30 pcs consecutive.
H
Hedape
Re: P Values
We had a discussion today at work about p-values in relation to ppk. Someone said if the ppk value is above a certain value then the p-value can be disregarded, that they were told this by Ford. I went through the Ford supplier manual and cannot locate information in regard to this relationship and believe that it doesn't exist. I think you could have a p value less than .05 and still have a ppk that is way above 1.67. Anyone hear of this before?
We had a discussion today at work about p-values in relation to ppk. Someone said if the ppk value is above a certain value then the p-value can be disregarded, that they were told this by Ford. I went through the Ford supplier manual and cannot locate information in regard to this relationship and believe that it doesn't exist. I think you could have a p value less than .05 and still have a ppk that is way above 1.67. Anyone hear of this before?
H
Hedape
For hypothesis testing. Capability six pack in minitab gives us the result.
The Ppk of any process is irrelevant to the p value in a hypothesis test. A small Ppk doesn't make the p value irrelevant at all. Ppk only indicates the spread of the process vs the specifications. a Hypothesis test is used to determine if the results of two experimental treatments (or conditions) are statistically significantly different from each other. NO relationship exists other than the SD of the two process conditions contribute to the mathematical formula that calculates the p value.
Can you elaborate on the discussion?
Can you elaborate on the discussion?
Minitab's capability six pack only has 1 p-value, and that's for the normal probability plot.
That person probably meant that if your process is highly capable that the assumption of normal data no longer matters. A lot would depend on why the data were non normal. If it were due to an unstable process, I would be very careful making that assumption. If it were due to mixed but stable process streams, or a naturally occurring non normal process, I would definitely place normality of the data lower on my list of things about which to worry.
However, in regard to your original question, I would be very surprised to find that Ford ever stated this in written form. An individual Ford employee may have expressed their opinion as to this.
That person probably meant that if your process is highly capable that the assumption of normal data no longer matters. A lot would depend on why the data were non normal. If it were due to an unstable process, I would be very careful making that assumption. If it were due to mixed but stable process streams, or a naturally occurring non normal process, I would definitely place normality of the data lower on my list of things about which to worry.
However, in regard to your original question, I would be very surprised to find that Ford ever stated this in written form. An individual Ford employee may have expressed their opinion as to this.
ah. Thanks Miner! I don't have Minitab and am unfamiliar with their 'six pack' and since I don't calculate capability indices I don't naturally think about the Normality test.
If this is the case then from a practical standpoint a properly designed study that is representative of the process variation and that has a very large Ppk number would still be highly capable even if the process wasn't 'Normally' distributed.
If this is the case then from a practical standpoint a properly designed study that is representative of the process variation and that has a very large Ppk number would still be highly capable even if the process wasn't 'Normally' distributed.
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