Chi-squared test - Post 16 Biology (A Level, Pre-U, IB, AP Bio)

[@NuclearCashew]

The editing and the way you explained everything made this all the more easier to learn from. Thank you very much!

[@cyclqal]

OMG I was so utterly confused for so long and this tutorial was relaxing, easy-paced, and actually enjoyable. This explained it and the chi-square is making sense now. Thank you!

[@alikazi3792]

The editing and the way you explained everything made this all the more easier to learn from.

[@serhanummar9782]

3 squared is 9, not 6. I was confused why I'm getting different chi-squared value until I review the table. :-)

[@MrExhambio]

Yes sorry

[@skuasomething3104]

if anyone else noticed that their answer was different then his its because. in the example he said 3 squared was 6 (which should equal 9) also the observed amount of green wrinkled goes from 37 -> 38 (it should be 37) therefore O-E should = 2 and O-E^2 should = 4. Both of these result in his answer being wrong. (x^2) should be = 1.764 not 1.821
you would still accept the null in the end regardless. And overall this video was very helpful but I just wanted to clarify incase anyone else noticed that their answer was different then his and wasn't sure why :)

[@jevjev6755]

Thank you! I finally understand this. And don't worry the minor discrepancies did not take away from lesson.

[@zunix1441]

After watching couple of videos on this topic, you turn out to be the life saver finally. Many many thanks🙏

[@Lllukasko]

my man saving life with these

[@abdullahhussain9589]

Finaalllly!!!!! Something clear and worth watching. Thank yoooouuuu !!!!!🤩🤩🎉🎉🎉🎉👍👍👍💯💯💯💯💯💯

[@forrdera]

the only helpful chi square video out there, keep it up

[@ao_mine5112]

Hi. How do we find the expected values from the observed values? I am stuck at this point.

[@vaishalijha4260]

in this case, the expected value is a well known ratio in mendelian genetics. It's called the 9:3:3:1 ratio resulting from a dihybrid cross. Apply that ratio to the total number, and there are your expected values. correct me if I'm wrong cause I'm only an ap bio student right now

[@marquianiah7213]

​@@vaishalijha4260 BROO OMG U JUST HELPED ME

[@nicolemcintosh7517]

@@vaishalijha4260why do you use that ratio?? Are there any other ratios you would use in different scenarios and how do you determine when to use which one??

[@natashaaini6060]

why is 1.821 between 1 and 1.42? shouldn't be between 1.42 and 2.73?

[@muhammadaalyan1113]

Because that is X squared. If you square root 1.821 you get 1.349 which lies between 1 and 1.42. Hope that helps.

[@eviemannakee5352]

Omg this makes so much more sense thank you :)

[@edwardjosephdzongololo4356]

thank you so much i was having problems to understand this now its crear

[@aceayade1770]

thank you for this! such an amazing video

[@simranmehta9306]

was really good, but you said that 3 squared was 6

[@MrExhambio]

🤦‍♂️ sorry there are a couple of silly mistakes in here but the principles remain the same

[@navjotsingh2251]

Mr Exham Biology don’t worry, in some weird alternate universe 3 squared is 6🤪😅

[@La..la..]

Excuse me, where is the ration for the expected coming from?

[@prorangerr]

thats what im confused on

[@abdullahhussain9589]

That was made up in the question. Do you remember the total? The question wants the expected results to have the values of each category split within the given ratio

[@Isijejejsop]

It’s from the expected Mendelian ratio, 9:3:3:1

[@vaishalijha4260]

in this case, the expected value is a well known ratio in mendelian genetics. It's called the 9:3:3:1 ratio resulting from a dihybrid cross. Apply that ratio to the total number, and there are your expected values. correct me if I'm wrong cause I'm only an ap bio student right now

[@funcenter5256]

The mendelian ratio is 9:3:3:1
Sum up these numerical values 9+3+3+1=16
Now first value is yellow round seeds total seeds are 560 .
Yellow round seeds are9/16 multiply it with total number of seeds 560.
9/16×560= 315(expected value)
Similarly yellow wrinkled seeds,
3/16×560=105
Green round
3/16×560=105
Green wrinkled
1/16×560=35.

[@mezzen7342]

really made it easy! bless you

[@sonitclef8675]

3:29. Is the observed for green wrinkled supposed to be 37? Because when u add the observed up it equals 561. Idk 😐

[@sonitclef8675]

I got 1.764

[@MrExhambio]

Yes! There is a mistake in this video, well done for spotting it (not that it was deliberate)!

[@muhibwenancy8915]

@@sonitclef8675 it's 0.51

[@mdaniels6311]

What situations would lead to the null hypothesis being wrong, from a genetic POV? What went wrong?

[@SrApolloHG]

Thank you! Loved this I understand it perfectly now

[@cghvhh8650]

Is the null hypothesis talking about the difference that was made (1.something) that should have been zero (and that this zero is the null hypthesis) and with the value that we got out of the equation stating that this difference is due to chance/error? Since it is lower than the 7.something?

[@fanfanaquatic2783]

The value of (O-E)2 for green wrinkled should be 9, not 6, right?

[@skuasomething3104]

yes but he also messed up before then and O-E should be 2 not 3 so (O-E)^2 shoud be 4

[@adelinevick4471]

i love the slide with the big WOW!

[@theodoresweger4948]

Beautifully done, I gota slightly different Chi sq, your numbers changes from 37 to 38 between 2:59 and 3:61.

[@theodoresweger4948]

(got a not gota)

[@amirah3791]

hi! is the probabilityy always going to be 0.05? unless specified otherwise i suppose

[@rosazhang4953]

What does“degree of freedom”mean?And why it should be n－1? I'm a little confused about it...

[@skuasomething3104]

hope you figured it out by now but it essentially means how much "wiggle room" you have. if you have more traits then you get a little bit more wiggle room, and it should be n-1 since that's the equation to find out how many degrees of freedom you have. N = #of traits so to put it simply your degrees of freedom is one less then the total number of traits you have !

[@oliverspraguekelly6754]

Normally with the expected value don't you add up all the total observed and divide by the number of possibilities which is 4. so all expected would be 140?

[@GamingGuyGus]

just do what he says and you will be fine

[@alkimarea7702]

To find E you would do the ratio of a specific phenotype divided by total ratio multiplied by total observed, eg. 9/16 * 560 = 315

[@kaipark6126]

@@alkimarea7702 thanks a lot

[@abdullahhussain9589]

Yes we can do it this way. I learnt it your way at school too

[@abdullahhussain9589]

Yes but he was specifically referring to an example question. In this case the question asks to put the total within the ratio given

[@LookAtTheStars19]

Thank you very much ❤

[@cha0spretzel-534]

so glad i found ur channel 😁

[@niallkeane3794]

thanks for the great vid. however on the table u put 3 squared as 6 when it is 9 (3x3x3)

[@MrExhambio]

Yes sorry, spotted that one

[@muhibwenancy8915]

@@MrExhambio kindly explain on how you found the expected

[@theodoresweger4948]

The 38 and 35 got .257 but otherwise well-done thanks...

[@derrickhoward1367]

Great explanation but it appears that a few numbers are off.

[@alexiaplacinta5468]

Do we have to remember that ratio ?

[@muqtaryusuf9756]

3:28 3 squared is 9 not 6 :)

[@amnashaikh-sl1qi]

thank you!!

[@mohammedyehya5231]

That was amazing

[@winnieyu3341]

very confusing??? Where did you get the expected data for each one???

[@jonathans.3875]

Winnie Yu
The example tests if the observed traits are inherited in the typical Mendelian way. If this is the case, a ratio of 9:3:3:1 of the respective phenotypes is expected. Using this ratio (which is based on the basic principles of inheritance), the expected count for a given number of observations can be calculated. The actual calculations for the given example would be (560/(9+3+3+1))*9 for yellow round, (560/16)*3 for yellow wrinkled and green round respectively and (560/16)*1 for green wrinkled.

[@teecee6655]

@@jonathans.3875 Thank you!!!!!

[@muhibwenancy8915]

3²=9

[@gollygee3651]

this actually helped wtf

[@jvauxholder651]

cool guy