Questions tagged [students-mistakes]

For questions investigating students mistakes, clarifying their origin and asking for advice to fix or improve the mistakes.

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76 votes
11 answers
12k views

Whence the "everything is linear" phenomenon, and what can we do about it?

$$ \color{red}{(a+b)^2 = a^2+b^2}$$ $$ \color{red}{\sqrt{x^4+y^4} = x^2+y^2} $$ $$ \color{red}{e^{t^2+C} = e^{t^2}+e^C}$$ I've observed this phenomenon -- wherein, implicitly, students say, "...
Brendan W. Sullivan's user avatar
27 votes
9 answers
3k views

Teaching students to find and correct their own errors

Many students have a fairly good grasp of the topics they are learning but fall down because they miss fatal errors in their work. Some don't check for errors at all, while many simply can't find them....
DavidButlerUofA's user avatar
33 votes
14 answers
2k views

Revisiting topics from previous courses [closed]

I teach calculus to students who have almost all taken calculus before. (Primarily first-year college students who took calculus in high school but didn't perform well enough to skip the course.) ...
Henry Towsner's user avatar
21 votes
5 answers
785 views

How students write their work, and learning outcomes

While teaching students mathematics, I have noticed that some seem sloppy in the way that they write down their work. For example, a student is given a question: What is the area of the rectangle? <...
ctrl-alt-delor's user avatar
37 votes
7 answers
5k views

A Lexicon of Math Mistakes

Neil Postman wrote an interesting (and freely available) article called "The Educationist as Painkiller." I highly recommend you read the article for your own enjoyment and as a background to this ...
David Ebert's user avatar
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33 votes
11 answers
8k views

How can I teach my students the difference between a sequence and a series?

Sequences and series are related concepts but differ extremely from one another. I feel that students in integral calculus frequently mix them up. Part of the problem is that: Sequences are usually ...
Brian Rushton's user avatar
25 votes
11 answers
3k views

Redundant zeros

How to convince a middle school student that $0.50=0.5=0.500=\cdots$? I used the fact that $0.50=\frac{5}{10}+\frac{0}{100}=\frac{5}{10}=0.5$ but that far from intuitive. Then I tried to explain ...
user5402's user avatar
  • 1,528
20 votes
2 answers
468 views

Literature on learning from errors in mathematics

In teaching undergraduate mathematics, I implemented some strategies to encourage the students to look at errors they made or at "typical errors" in the current topic. One attempt was to compile a ...
Christian's user avatar
  • 544
6 votes
1 answer
713 views

Propositional and predicate logic, with quantifiers: Is there any research when it is ideal to explicitly teach in mathematics education?

In terms of helping students to understand propositional and predicate logic, with quantifiers, is there any research regarding when it is most advantageous for students studying mathematics, to first ...
amWhy's user avatar
  • 2,095
37 votes
4 answers
3k views

Taxonomy of bad proofs

I am interested in finding examples of poorly written proofs that exemplify the types of mistakes made by undergraduate students in their first year or two of writing proofs. I am interested both in ...
Patrick Lutz's user avatar
25 votes
7 answers
3k views

How do you coach students who often make small errors?

Some students are prone to making small calculation errors. Not errors in understanding, but errors like adding or multiplying integers incorrectly, or dropping a negative sign. Unsystematic errors in ...
Mike Pierce's user avatar
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21 votes
5 answers
4k views

Grating mathematical phrases---How to correct?

As mathematics educators, we all have come across students using mathematical notation incorrectly (looking at you, $\frac{d}{dx}$ vs $\frac{dy}{dx}$ or $\frac{\infty^2}{\infty}$). My question focuses ...
erfink's user avatar
  • 1,129
14 votes
2 answers
1k views

How does a reliance on calculators affect student performance?

Overheard in the Math Office while another Professor was helping a student with Statistics: Always use a calculator when doing decimal arithmetic because you'll eventually make a mistake if you do ...
Andrew Sanfratello's user avatar
8 votes
3 answers
1k views

What are some common ways students get confused about finding an inverse of a function?

What are some common ways students get confused about finding an inverse of a function? One I can think of is conflating multiplicative inverses of rational numbers with functional inverses. e.g. ...
Eleanor Hankins's user avatar
5 votes
7 answers
463 views

Category mistakes regarding symbols and their impact on math (mis) understanding. ( Object symbol/ sentence symbol confusion)

A friend of mine that teaches math has made many times the following experiment : drawing two circles on the blackboard representing two sets A and B such that A and B are disjoint writing on the ...
user avatar
35 votes
1 answer
2k views

Metonymy in mathematics

Metonymy is a figure of speech where a word or another expression is used to mean something other than its literal meaning. This phenomenon is not restricted to the "usual human languages" (such as ...
Joonas Ilmavirta's user avatar
33 votes
3 answers
2k views

Near-universal student mistake on $\lim_{x\rightarrow\infty}e^{x+1}/e^x$

On a recent first-semester calculus exam, I gave a bunch of limits. The student was supposed to use L'Hospital's rule if possible, or if not, explain why it didn't work and evaluate it by some other ...
user avatar
32 votes
23 answers
8k views

Quote to show students don't have to fear making mistakes

I have some high school students which seem to be afraid of making mistakes. They are hesitant to make exercises in class because they want their course notes to be super clean, without any mistakes. ...
dietervdf's user avatar
  • 431
29 votes
6 answers
8k views

Misuse of parentheses for multiplication

I'd like to raise the issue of constant misuse of parentheses in the U.S., and I'm wondering if anybody else shares the same feelings, has had the same issues, knows any history behind it, and can ...
zipirovich's user avatar
25 votes
5 answers
1k views

A Series of Unfortunate Examples!

All of us know, when teaching, the "right" choice of examples is important. Though, making the "right" choice is one of those things that are easier said than done. Here is the ...
Amir Asghari's user avatar
  • 4,428
23 votes
5 answers
1k views

Students using ambiguous notation

I've noticed that many of my calculus students (all college students) will write, e.g., $1/3x$ to mean $(1/3)x$. This is an inherently ambiguous notation which I'd like them to avoid. Is simply ...
Avi Steiner's user avatar
22 votes
3 answers
775 views

How can I discourage proof by patchwork?

I have a student who is working in their spare time on proving or disproving a conjecture of the form $$\exists x.\forall y.\phi(x,y).$$ Right now their strategy is to construct an $x$ and then show ...
forritari's user avatar
  • 323
21 votes
7 answers
5k views

Should students be told they're wrong

I base this question off where I got my motivation for math and science. Throughout several attempts in my junior years, I was able to design a perpetual motion machine, design a free energy device, ...
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21 votes
9 answers
2k views

Why do students have problems with showing that something is well-defined? How can this be improved?

I see a lot of students struggling when they have to show that something is well-defined. I have the feeling that this is often not understood. Two examples: When defining a sequence $x_n= g(x_{n-1}...
Markus Klein's user avatar
  • 9,438
19 votes
5 answers
2k views

Common misconceptions in high school probability curriculum

I am teaching probability to high school students. The material we are covering is pretty standard and includes: Introducing how to calculate the probability of events, e.g. coin flips, card draws, ...
Improve's user avatar
  • 1,881
18 votes
4 answers
2k views

Why do students only see the last term of a sum abbreviated with an ellipsis?

It's very common in learning mathematical induction to prove statements like $$ 0^2+1^2+2^2+\cdots+n^2 = \frac{n(n+1)(2n+1)}{6}.$$ I've found that very frequently, on this sort of problem, when ...
Mike Shulman's user avatar
  • 6,570
17 votes
1 answer
447 views

Addressing fundamental math errors

I am looking for ways I can correct fundamental math mistakes. I am currently tutoring someone taking a course which is a cross between first year calculus and grade 12 functions. In high school he ...
Gareth Shepherd's user avatar
15 votes
5 answers
2k views

How to deal with answers containing completely off-topic/random/very wrong arguments?

It often happens that students answer (partly) a questions in an exam (lets assume this part is okay), but then add something completely off-topic or something very wrong in their answer (see examples ...
Markus Klein's user avatar
  • 9,438
12 votes
2 answers
3k views

How are students messing up in this Khan Academy surface area problem? (right triangular prism: 3-4-5 triangular base, height of 11)

The following question appeared in this Khan Academy exercise in January 2017, and the actual data on the ten most frequent incorrect responses is shown below the question. What mistakes did students ...
Cameron Christensen's user avatar
12 votes
6 answers
2k views

Why does the widespread erroneous definition of "irrational number" persist without being taught?

Among the mathematically ignorant one often finds a mistaken proposed definition of "irrational number", which says that it is a number whose decimal expansion does not terminate or repeat. The ...
Michael Hardy's user avatar
11 votes
3 answers
642 views

Common phrases having different meaning

When talking with students it frequently happens that they misunderstand what you meant. The common example is the amount of rigor that one would consider "a proof", but there are other ...
dtldarek's user avatar
  • 8,947
9 votes
1 answer
1k views

Should $\varphi$ be monotone in the integration by substitution?

I'm trying to calculate $$\int_{\frac{-\pi}{2}}^{\frac{\pi}{2}}\sin t \cos^3 t\,dt$$ using integration by substitution $$\int_{\varphi([a;b])} f(x)dx=\int_{[a;b]} f\left(\varphi(t)\right)|\varphi'(t)|...
user5402's user avatar
  • 1,528
8 votes
1 answer
840 views

What goes wrong when students interchange "there exists" and "for all" randomly? How to fix this?

I think, it is a very common problem that some students have huge problems with definitions when there appears a quantification. Some examples: Of course the sequence is bounded, because every part ...
Markus Klein's user avatar
  • 9,438
7 votes
5 answers
834 views

What are some common fallacies students make when they learn $X$ concept?

What are some common mistakes students often make, which may seem logical at first? I'm a student myself, but I'm curious of what some of the most frequent mistakes which happens. I'm thinking of ...
Frank Vel's user avatar
  • 243
6 votes
3 answers
471 views

How can you elicit the $\log x = {\log} \cdot x$ error?

You know the error, when you're watching a student work through an algebraic calculation to solve for a variable trapped in the argument of a function, usually $\log$ or a trig function, and you watch ...
Mike Pierce's user avatar
  • 4,845
6 votes
8 answers
820 views

How much credit to give a short exam question with one error?

In comments here there seemed to be significant difference of opinion on how much credit to give to a short exam question with a single critical error in it. Consider the example of student work ...
Daniel R. Collins's user avatar
3 votes
2 answers
355 views

Common mistakes in probability

$\DeclareMathOperator\Var{Var}\DeclareMathOperator\Bern{Bern}\DeclareMathOperator\Pois{Pois}$Question: What not-trivial mistakes do students often make when solving problems in probability theory, ...
Botnakov N.'s user avatar