5 research outputs found
Modelling and Using Response Times in Online Courses
Each time a learner in a self-paced online course seeks to answer an
assessment question, it takes some time for the student to read the question
and arrive at an answer to submit. If multiple attempts are allowed, and the
first answer is incorrect, it takes some time to provide a second answer. Here
we study the distribution of such "response times." We find that the log-normal
statistical model for such times, previously suggested in the literature, holds
for online courses. Users who, according to this model, tend to take longer on
submits are more likely to complete the course, have a higher level of
engagement, and achieve a higher grade. This finding can be the basis for
designing interventions in online courses, such as MOOCs, which would encourage
"fast" users to slow down
Fluid Velocity Fluctuations in a Suspension of Swimming Protists
In dilute suspensions of swimming microorganisms the local fluid velocity is
a random superposition of the flow fields set up by the individual organisms,
which in turn have multipole contributions decaying as inverse powers of
distance from the organism. Here we show that the conditions under which the
central limit theorem guarantees a Gaussian probability distribution function
of velocities are satisfied when the leading force singularity is a Stokeslet,
but are not when it is any higher multipole. These results are confirmed by
numerical studies and by experiments on suspensions of the alga Volvox carteri,
which show that deviations from Gaussianity arise from near-field effects.Comment: 4 pages, 3 figure