The ideal teaching assistant:
Marks fairly without bias towards
individual students
Marks consistently with other teaching
assistants
Relates laboratory work to professional
practice
Shows good knowledge of techniques and
skills
Gives clear explanations
Criticises constructively with clear
explanation of errors
Supports students and helps their self
confidence
Admits their own mistakes
Is approachable to the students
(From Engineering Professors’
Council workshop on
"Effective Laboratory
Teaching")
Helping students to solve problems -
asking questions
The objectives of the demonstrator here
is to act as ‘facilitator’
rather than an expert, which is best
done by asking the right sort of
questions.
Closed questions
Those designed to produce a ‘yes’ or
‘no’ answer or to check facts
‘How many times did you -?’
‘Have you completed the task?’
Open questions
Are designed to encourage narrative,
exploration, reflection, description.
‘Tell me what happened.’
‘What have you done so far?’
‘What seems to be the problem?’
‘What might you do next?’
‘Where might you find the information?’
‘How will you know if it is working?’
Hypothetical questions
Are designed to suggest possible options
‘What do you think will happen if -?’
Reflective questions
Are designed to encourage further
thinking, without breaking the line of
thought
‘You said the liquid turned blue -’
‘You said you didn’t understand the
reaction -’
‘Can you say some more about that -?’
Questions to avoid
Leading
questions-
Questions which are really statements
‘I’d have thought that -, wouldn’t
you?’
Multiple questions
Piling one question on top of another so
that the person does not know which one
to
answer first
Case study: Statistics practical ‘t’
test The students in this practical have
been asked to devise an experiment
involving the use of the ‘t’ test.
Example of the use of a ‘t’
test
In a study of household waste
in the Midlands, one week’s waste was
weighed from a sample of 35 households
whose waste
was collected in plastic bags and
a sample of 32 households with wheeled
bins. Using the ‘t’ test it is
possible to test the
hypothesis that households with
wheeled bins generate more waste than
households with plastic bags.
The teaching assistant, Marrk, is
working with 2 students on their
problem. Read the transcript (which
includes most of the discussion) and
think about the following questions:
What is the
teaching assistant trying to do?
How does his
use of questions help or hinder the
process?
What other
strategies might he have adopted?
Do you have any
comments on the design of the practical
activity for teaching the ‘t’ test?
"Student A
We are testing whether water speed -
water flow speed in a river increases
during
winter months, therefore changing the
biodiversity of the river
Mark
So what are you measuring first of all?
Student A
Water speed at depth and on the surface
Student B
In the summer and winter months
Mark
So, wow, you are measuring everything!
Student A
Yes - we’re measuring it throughout
the year
Mark
So you’re going to measure water speed
in summer and winter. What else are you
measuring?
Student A
Measuring at a certain depth and on the
surface
Mark
So you’re measuring water speed at two
different times of the year? And you’re
measuring water speed at the depth and
at the surface
Student A
We need to see whether the species
changes, the diversity of the species
changes
from winter to summer
Mark
So you are also going to measure for
each of these four different conditions.
Diversity at each. All of a sudden - How
are you going to be able to separate the
effects of summer or depth. How are you
going to separate the effects of the
time of
the year?
Student B
- have to be kept constant. Just what
you’d be doing would be measuring the
water
speed at the summer and winter - you’d
be saying, I suppose, summer, winter,
summer with more speed should be slower
Mark
Your ‘t’ test is for comparing two
different needs, for two different
treatments. Just
simplify your whole experiment first of
all and give me a simplified version of
this that
is suitable for the ‘t’ test.
Student B
Why?
Mark
Because all of a sudden you’ve got all
these things that were changing. I’m
trying to
get you to narrow it down a bit.
Student B
Right. OK
Student B
Just take those two out then
Student A
Yes, take those two out
Mark
OK, so -
Student A
We just do it at a random depth
Mark
Presumably these are two different
experiments. You want to have the effect
of
water speed on diversity and you are
going to look at that in the summer and
the
effects of water speed on diversity in
winter? Are you?
Student B
Yes
Mark
So how would you do one of those?
Student B
You’d get your water speed slowly -
Mark
Right
Student B
And you -, I suppose you take the
averages of every day
Mark
Right
Student B
You’d er - you remember the eco system
thing where you had to get a net and put
it
in the water?
Mark
So you’d use a net to catch -?
Student B
You could drag it along and use the flow
chart method
Mark
So you are going to have a big long list
of day and diversity. Is this for one
river? So
day, diversity and water speed. How are
you going to know when you can do our
‘t’
test because you’re going to have
presumably three sets of means. How are
you
going to know whether it’s the effect
of day of the effect of water speed?
Student B
Umm-..
Mark
Are you always going to go back to the
same place in the river because you
might
just be finding some sort of seasonal
change - So ‘t’ test is ... really
great for looking
at quite simple effects where you are
contrasting two different means. Perhaps
you
should just have the river and perhaps
you should just visit different sections
of it -
because at the moment you are not really
controlling for seasonal change. And it
would be really hard to know whether
seasonal change is causing the diversity
change or whether the seasonal change,
you know, different amounts of rainfall,
is
causing this, causing the change in
water speed
Student A
Then we could eliminate diversity and
just test whether the seasonal change
changes the water speed
Student B
-
Mark
So your experiment has come a long way.
I thought diversity was good. So now,
what are you explicitly going to test
and collect data for this ‘t’ test?
Student B
Water speed
Student A
Winter and summer
Student B
Or you could eliminate that and do it
the other way round; see if there is a
seasonal
effect on biodiversity
Mark
Could you justify it if you did think
there was a seasonal effect on
biodiversity? Is it
so obvious that you wouldn’t really be
able to justify going and proving that
in winter
there are less species than there are in
summer?
Student B
So you have to go for water speed -
Mark
Well, I really like this. I really like
this because you said that right from
the very
beginning that effect diversity were
time of year - summer and winter, speed
of water
and depth in the water column - so you’ve
got three factors there so if you narrow
it
down to one - which is water speed and
diversity -
Student B
Yes
Mark
You could have presumably - have you
done A Level Biology?
Student B
Yes
Mark
Have you done experiments where you’ve
got fast flowing rivers, quite still
pools and
you sample the number of species in
those different environments.
Student B
No not these - we just went to a lake
and just puddled around there for a
while.
Mark
Caught what you could?
Student B
Yes
|