Week 11
We looked at the Poisson and Normal Distributions.
Week 12
We will look at sampling and hypothesis testing.
Week 13
We will go through last year’s exam on the board and then I will answer your questions if there are any. If there are none I will help one-to-one.
Study
Please feel free to ask me questions about the exercises via email or even better on this webpage.
Student Resources
Please see the Student Resources tab on the top of this page for information on the Academic Learning Centre, etc.
2 comments
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December 3, 2015 at 8:35 am
Student
Hi J.P.,
Would there be a possibility of me getting comments on my 2 projects as I didn’t keep a record. They might be useful for revision.
Thanks.
December 3, 2015 at 9:15 am
J.P. McCarthy
Assignment 1
Question 1
(g) In this question you were asked to use your model
to extrapolate the consumption for this year and 2020. Your model, for Sweden, was
This
is the consumption
years after 2005. The
is like the
— it denotes that
depends on
— it does not mean
.
Question 2
(j) In this question you were asked to find the slope of your parabola
at
. Now should have worked with
as you had found but instead you differentiated
In this case
was a constant and so the derivative should have been
not
as you had.
Question 3
(e) You are given (span,max deflection) data and are asked to to a log-linear least squares fit. First you linearised the relationship
successfully as
Note this is in the form
and so if you plot
vs
you get data that looks like a straight line to which you can fit a line and so find
and
.
Instead of doing least squares with
you just did least squares with the original data… the original data does not have a straight-line relationship and so what you do doesn’t really make any sense.
The examples on p.37 to 42 of the notes show what you need to do with these.
Question 4
(h) You were supposed to use your model
to find the grain size
such that
. Similarly to the issue with Q. 1(g),
just means that
depends on
—
. You needed to find the
such that
was equal to fifty. Your model was
so you needed to solve
Assignment 2
Constant Load on a Simply Supported Beam
Question 3 (c)
To see why
for simply supported please see the bottom of p.99
Question 6 (f)
In your comment to your graph you should have noted that the maximum bending moment takes place where the shear crosses the
-axis — aka where the shear was zero. You could have also said that the bending moment was zero on the endpoints.
Linear Load on Fixed Ends Beam
Question 5
You find
and
You take
— correctly as it is fixed ends.
Now you calculate
and
(with rounding errors too) and you get
as I said you have rounding errors and you should use fractions.
Now you went on to solve these as simultaneous equations… but these aren't equations at all so you were bound to go wrong and you did.
See
Now we know that both
and
and so
and
… so what you should have had was, remembering these are
and 
These are genuinely equations. See the marking scheme on p.93 of the notes to see this done properly.
Question 6
First of all you wrote
are equal to zero…
is not the same as 'and'! You should write
and
are equal to zero or
not
… you can have
with neither equal to zero…
Your picture of a beam with fixed ends and
on the left and
on the right showed a lack of understanding. Please see the discussion starting on p.99 and running into p.100 to understand this properly.
Question 7 (a)
You were supposed to find the location of the maximum bending moment. You found it to be at
or
— yet your beam had a length of only four and so neither of these are on the beam… this should have told you that something was wrong.
Question 8 (a)
In your comment to your graph you should have noted that the maximum bending moment takes place where the shear crosses the
-axis — aka where the shear was zero. You could have also said that the bending moment was not zero on the endpoints as the beam was fixed ends.
Question 8(b)
Your graph is clearly wrong… have a look at it. It should look like Figure 2.26 on p.91 of the notes.
Cantilever with Point Load(s)
Question 3
Non-Integrable Load
Question 1
It wasn't a UDL. There is even a picture of the load on the previous page.
Question 9
You never used the chain rule. You had
To differentiate this you can fix the constant and then when you are differentiating look on the function as:
Using the Chain Rule:
The derivative of the inside can be carried out with a second chain rule or else after multiplying out.
This is first year material but as I have discussed in class semesterisation and other issues means that ye have forgotten a lot of this stuff.