## Understanding the p-value – Statistics Help

One of the most important concepts in statistics is the meaning of the P-value. Whenever we use Excel or other computer packages to analyse data, one of the key outputs is the p-value or sig. In formal terms, The p-value is the probability that, IF the null hypothesis were true, sampling variation would produce an estimate that is further away from the hypothesised value than our data estimate. In less formal terms, The p-value tells us how likely it is to get a result like this if the Null Hypothesis is true. We will now go through this step-by-step with an example. Helen sells Choconutties. Recently she has received complaints that the choconutties have fewer peanuts in them. than they are supposed to. The packet says that each 200g

packet of choconutties contains 70g of peanuts or more. Helen can’t open up all the packets to

check as then she wouldn’t be able to sell any. So she decides to use a statistical test on a sample of the packets. The null hypothesis, often called H “nought” is the thing

we’re trying to provide evidence against. For Helen, the null hypothesis is that the

choconutties are as they should be. The mean or

average weight of peanuts in the packet is 70 grams. The alternative hypothesis called H1 or HA is what we’re trying to prove. The customers had complained that the weight of peanuts is less than what it should be. So the alternative hypothesis is that

the average rate of peanuts is less than 70 grams. Helen decides to use a significance

level of 0.05 if the P-value is lower than this, she will reject the null hypothesis Having decided on her hypotheses and on the significance level Helen takes

a random sample of 20 packets of Choco-nutties from her current

stock of 400 packets. she melts down the Choco-nutties and weighs the peanuts from each packet. If all of the values were lower than 70

grams with a mean of 30 grams for instance,

it will be quite obvious that the bars did not have the required number of

peanuts. It is very unlikely that you’ll get 20

packets with a mean of 30 grams if the overall mean of all the packets in the

population is 70 grams Conversely, if all the values of the 20

packets were much higher than 70 grams, it would be obvious that there were

enough peanuts and that there was nothing to complain about. However, in this case the 20 packets

contain the following weights of peanuts and the mean is 68.7 grams. This caused Helen to ask herself: “Does this provide enough evidence that the bars are short of peanuts or could this result just be from luck?” She

asks her brother to use Excel to find the p-value for this data, comparing with the mean of 70 grams. The P value is 0.18 Judging from the data that we have,

there is an 18 percent chance of getting a mean as low as this or lower if there is nothing wrong with

the bars. That is, if the null hypothesis is true and the mean weight of nuts is 70 grams or more. This P value of 0.18 does

not provide enough evidence to reject the null hypothesis. In this case helen does not have

evidence to say that the bars are short of peanuts. This is a relief! The smaller the

p-value is, the less likely it is that the result we got was simply a result

of luck. If the P value had turned out to be very

small we then would say that the result was

significantly different from 70 grams. In general we start by saying that the

null hypothesis is true. We take a sample and get a statistic. We

work out how likely it is to get a statistic like this, if the null hypothesis is true. This is

the p-value. If the P value is really really small, then

our original idea must have been wrong, so we reject the null hypothesis. P is

low, Null must go. A small P value indicates a significant

result. the smaller the p-value is the more

evidence we have that the null hypothesis is probably wrong. If the P-value is large, then our original

idea is probably correct. we do not reject the null hypothesis.

This is called a nonsignificant result. The P-value tells us whether we have

evidence from the sample that there is an effect in the population. a P-value less than 0.05 means that

we have evidence of an effect. A P-value of more than 0.05 means that there is no evidence of an

effect. Sometimes a significance level different from 0.05 is used, but 0.05 is the most common one. This video uses plain language to get

difficult ideas across. Some terminology might be viewed as

incorrect by a rigorous statistician.

## Comments

(100 Comments)

I clicked cause I saw Mello

Thanks very much it is so helpful

Lol Funny and simple way to explain it, very clear again!

I finally think I understand it.

incredible!!

If the P is low, drop the Ho. Best way to get giggly highschoolers to remember it.

Think about area on the graph

I'm sorry but this is a very bad explanation/visualisation. It can only be explained using a normal distribution.

What is the name of the chocolate seller?

Please see the 2016 American Statistical Association statement on "Statistical Significance and P-Values." The world's foremost experts address the problem of common misinterpretations of the P-value. The P-value does not tell you whether the data are due to random chance or whether the null hypothesis is true or false. It is a measure of the goodness of fit between the observed data and the statistical model.

In General haha you killed me there

I loved this lesson. Not only was it super educational and valuable in that aspect, but it was clever and it made me laugh really hard. You had my attention the entire time. Thanks XD

Why don you weight the nuts bifore you put it in the chocolate.

Oh my goodness bless your soul

This is an excellent video. Thank you!!

Thank you. I finally understand what p-value means.

This is really good, and funny, which helps. I'm new to statistics – how come they just don't call it the "hypothesis"? What's with "Null" adjective?

Such a clear explaination ! Thank you a lot 😀 !

very helpful to get the concept

what does the significance mean, and why is it 0.05? can you just pick a random significance level???

YOu screwed up this explanation by confusing the issue with Null Hypothesis and which side of the argument you are on, without explaining it.

This wasn’t a clear explanation. What about t-score? You’re confusing p-value with t-score.

The p-value is used to calculate the t- score number on the table. A two tail hypothesis requires t-alpha/2.

What about the degrees of freedom?

You have totally confused the issue of hypothesis testing.

Good night!!!

You gave an a statistical example as definition. What is the definition of p- value?

P-value is the level of significance.

This is the definition of p-value:

The p-value is the level of marginal significance within a statistical hypothesis test representing the probability of the occurrence of a given event. The p-value is used as an alternative to rejection points to provide the smallest level of significance at which the null hypothesis would be rejected.

level of significance…

The null hypothesis is rejected if the p-value is less than a predetermined level, α. α is called the significance level, and is the probability of rejecting the null hypothesis given that it is true (a type I error). It is usually set at or below 5%.

super Like

But what exactly is p-value? Where does it come from?

Omg thank you for this!! We need more dumbed down videos like yours!!!

Great explanation. Just for clarification, the p-value came from using the statistical rules of a one-sample t-test? I've been a little mystified as to where the actual p-value comes from. I understand a low p-value means reject null. I've used the software to get a p-value. We must set up our problem appropriately and select the right statistical test which then yields a p-value?

The perfect video! I don't understand why college makes it sound like a concept of god; it's simple: if p is low, the null must go!

Thank you!

Extremely helpful n understandable.

Dr Nic should be getting sponsored by choco nutties!

best explanation.

Thank you.

totally lost by this … why is this so hard for me to get.

Helen scares me.

Oh dear.

Null hypothesis means that you are testing your variables at 0.05 (%95 level) significance level your variables if they are correct to estimate your model or sample then youe variables is not equal to zero,they are affecting your sample which null hypothesis was Ho:B1=B2=0 this implies if you have right variables to solve your model then you reject null hypothesis because b1 and b2 has an effect on your model.p value determines your null hypothesis is really true or wrong.So if mean average of your variables more than 0.05 in p value than you have to accept that your variables are wrong and has no effect or your null is true.

wait so how did she get 0.18? im confused

Great video ! It actually helped me a lot. Just subscribed the channel. Keep up the good work. Thanks.

is that posture a Phoenix Wright reference lol

I enjoy your style of speaking. Definitely subscribing

Helen looks like a bitch.

I little bit confused when it said we want to proof the alternative hypotheses however all of the video is saying that we will be happy if the null hypothesis is true

I believe explaining HOW to calculate the p-value would have made it a bit better. Thumbs up anyway

Best p value video on the internet. I want some Choconutties

The p-value is used to determine if the outcome of an experiment is statistically significant. A low p-value means that, assuming the null hypothesis is true, there is a very low likelihood that this outcome was a result of luck. A high p-value means that, assuming the null hypothesis is true, this outcome was very likely.

Did Iggy Azalea narrate this

Gooood

still don’t get it

Frieken smart lady

I just dont understand why Helen is allowed to define the significant level (=0.05) and the amount of chocolates she wants to test (=20) by herself to proof her chocolates are alright. She could have decided to take a random sample of 5 chocolates and win the case anyway. It would make so much more sense when the judge decided the parameters.

Either I dont understand it, or your example has some flaws.

I love this channel 💕

I’ve come back to this about a 1000 times

Great Video! Thanks.

I disagree. This is why studies are often wrong. Raise the arbitrary significance level to 18% and you get a different conclusion. The truth is too many bars have too little peanuts and even the average is too low. Most should have more than 70 grams or they should put a different number on the package. No amount of statistical juggling with numbers is going to change the truth that there are too few peanuts.

Tính sao ra được 0.18 vậy ta

Wonderful explained!! Those wonderful people who take from their time in order to help others..

God bless you!

THANK YOU

Thats not helen… THATS MELLO FROM DEATHNOTE xD

Thankyou soo much

Wow. TY. I only need to know this 1/8th of test and I WILL NEVER need again. TY for explaining simply. It made the more complex explanation understandable,

If I read an article that gives a statistic then in parenthesis gives a p value of <0.05 does that mean the information before the p value is wrong or that the information is correct ?

example: The CHHIPS (Controlling HTN and Hypotension Immediately Post-Stroke) trial compared the effects of lisinopril, labetalol, and placebo on the 2-week death or dependency rate when administered between 5 and 36 hours from the onset of ischemic or hemorrhagic stroke. The decrease in SBP was significantly greater in the combined active treatment group than in the placebo group during the first 24 hours [difference: mean=10 mm Hg, 95% confidence interval (CI)=3-17 mm Hg; p=0.004]. However, there was no difference in the primary end point of the 2-week death or dependency rate within treatment groups or between the treatment and placebo groups.12

In the example above does that mean that there is a 95% confidence that the information about the difference in mean blood pressures in the two groups is likely wrong and that there is a difference in blood pressures that is different than 10mmHg either higher or lower?

Why are you talking to us in jargon? As though we know what 'null hypothesis' means

Great explanation

The video is wrong… for Helen's choconutties case, the null hypothesis should be that "they are short of peanuts" (the video says it is they are as they should be) !!!!

Loving the animations

Wonderful explanation !!

Yes, love this simple explanation!

Fair of you to throw in the disclaimer but that was really well explained. "If you can't explain it simply, you don't understand it well enough" – Einstein.

I really love your videos! brilliant work, but the choco-nutties are making me hungry! 🤤

This video makes me want to have some chocolate

(nice explanation btw)

Annoying video and annoying example

Hellen iS Pure EViL

Thanks I love it.

This is really awesome , Applause from Egypt 😃👌👍👏👏👏👏👏👏👏

I must be dumb. Damn immunizations. Lower iq

I liked your disclaimer, made me smile. Cool animations too.

Great example! Thank you 🙂

Where does the .18 come from? How did you calculate that?

Great explaination

tahnks for the ehlp

isn't it – the 0.18 is the probability of the mean being close to 70. so being higher than the 5%, the Hypothesis of 70 is not being rejected?

I need to show it to my girlfriend. Finally she'll believe that small p is good

Great Thanks form Greece =D

my goodness… you explained it too damn clearly. I have been looking all over youtube.. for a good explanation.

Very good explanation! Understood in under 10 mins with multiple replays.

Thanks for dumbing this down

i enjoyed watching this, thanks!

Thank you, I really liked the explanation!

thats really good explanation and animation too

im beginning to get it. thank you.

These vids are SO GOOD, love Helen and the choco nutties! xD

makes no fucking sense!!!!!

why does Helen's brother look like Edward Elric from Fullmetal alchemist?

XD

Made me hungry ! Now I want choco nutties.

Thank you

JFC, this was so extra

Amazing! Thank you!

Great video, ^^LoLz^^

After 6 videos I'll go to the store for choco nutties =D, or something simillar

Thanks for helping out with my college studies!