Miscellaneous Examples : Part 3 Video Lecture | Mathematics for GRE Paper II

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before watching this video please make
sure that you have all statistics part 1
to part many for saying the mean and
standard deviation of 100 observations
were calculated as 40 and PI point 1 by
a student who mistook the teens your 40
for inoculation we have to find the
correct mean and correct standard
deviation so one thing is clear in this
example that n is equal to hundred type
and we have incorrect mean and in kind
standard deviation so I will say X is
equal to 400 and this standard every
little fight for me what i incorrect so
i'll say i pi x is incorrect incorrect
me in the next second division now we
know that mean is nothing but 1 by n
into Sigma X I this small lovino correct
and we don't and incorrect mean you so
incorrect Sigma X is nothing but
anything to incorrectly incorrectly
value is nothing but n is 100 that turns
out to be incorrect song this is
incorrect song all right I hear it is
incorrect sound is this or I'll write
cross here about the terms is incorrect
incorrect service right now the correct
some parts the correction correction
will be in 4,000 you subtract soon as we
go further you subtract 50 anyway and 40
by because this guy miss 250 is you have
40 the correct value has forties will
add 40 and the in Chi pelvis will please
about the movie 50 so in your pocket I
think one thing is wrong you have to
replace you take out the wrong thing and
put the right thing so here or 7 take
out the wrong thing mounting is 50 and
put the
so the correct sum is nothing but three
nine correct therefore the correct me I
write correctly in the likelihood pigma
it is correct mean is nothing but three
nine nine zero by N and the number of
table is nothing but hundred the current
weight is nothing but thirty nine point
so this is 40 a go we have got the
correctly federally pointing now let's
find variance so for this is one
equation we have got now let's use the
other data which we have got the
variously down sorry
Saturday we should read up the standard
deviation is nothing but such general
formula 1 by n summation X PI square
minus 1 by n square summation of X Phi
holds 1 right and the whole thing in the
root actually this is what is the value
of variance
it rolls right and this is nothing but
me we can also say is nothing but mu
power 1 by n Sigma X square minus mean
square all right
because Sigma X I by N is B so this
becomes please good now let's use the
correct incorrect so first wisdom
incorrect incorrect piece incorrectly is
nothing but 5.1 this is equal to 1 by n
n is always valid actually into Sigma X
I Square this is incorrect a'right Sigma
X I self is incorrect so right now
infrared signal here - this and
encourage for everything is encrypted so
incorrect p square so in draperies 4640
spot the sortie so when you solve this
when you saw this I'll solve this so
this becomes 5.1 square or 5.1 square is
nothing but 26 point 0 1
twenty six point zero 1 is equal to 1
500 into Sigma X PI square that is
incorrect
- 1600 correct or you can say that Sigma
X PI square it is incorrect this is
equal to this value 1600 plus twenty six
point one in two hundred so what we'll
get is one six two six correct and that
is the information this is nothing but
my incorrect me sorry this into hundreds
of this becomes loose once these two six
zero one this is my incorrect me a link
in that so now what we have got we have
got incorrect values square some that we
have got correct also since we have done
this way correct sum is equal to total
sum - this does this similarly begin to
this way also correct Sigma it's PI
square that is nothing but Sigma X I
squared incorrect right - 50 square
because it has an incorrect plus four T
squared here as we same thing here and
she'd of square I was doing normal rates
correct service will do incorrect some
minus 50 plus forty also correct some
squares will do incurring some square
minus mu square by 4 - square right or
this is nothing but 1 6 - 6 is 0 1 minus
50 square that is 2 5 0 0 plus 4 T
squared is 16 and this value comes
opening 1 6 1 7
so I have got the correct some spot I
have got the correct some square I have
got the correct me the correct mean is
this this correctly and I have got the
correct some square also now using this
again find the value of correct Sunday
division its do that we know that
standard deviation is nothing but root
Sigma X square n minus M square this is
what people we know about this in open
up all these values so what do this will
put the value this value is summation of
correct X I square is one six one seven
zero one we have found this n is equal
to hundred minuses mean is nothing but
correctly is thirty nine point nine
square and the whole thing is Allah so
if we solve this this becomes one six
point seven point zero one minus this
becomes minus five ninety two point 1001
and this is root and this is nothing but
root 25 and the bottles so the correct
variances or the correct standard
deviation is fine if you want to know
correct standard a variance you can say
that this is nothing but Sigma square
that is Phi square that is 25 so correct
various is 25 and the correct standard
deviations very simple what we have done
we have just found you this formula
salvation we use this formula correct
sum is Purdue incorrect sub minus 50
plus forty and also correct summation X
I square is equal to incorrect sub X I
square minus 50 square plus 40 square
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