A longitudinal study (or longitudinal survey, or panel study) is a research design that involves repeated observations of the same variables (e.g., people) over short or long periods of time (i.e., uses longitudinal data). It is often a type of observational study, although they can also be structured as longitudinal randomized experiments.Longitudinal studies are often used in social-personality and clinical psychology, to study rapid fluctuations in behaviors, thoughts, and emotions from moment to moment or day to day; in developmental psychology, to study developmental trends across the life span; and in sociology, to study life events throughout lifetimes or generations; and in consumer research and political polling to study consumer trends. The reason for this is that, unlike cross-sectional studies, in which different individuals with the same characteristics are compared, longitudinal studies track the same people, and so the differences observed in those people are less likely to be the result of cultural differences across generations. Longitudinal studies thus make observing changes more accurate and are applied in various other fields. In medicine, the design is used to uncover predictors of certain diseases. In advertising, the design is used to identify the changes that advertising has produced in the attitudes and behaviors of those within the target audience who have seen the advertising campaign. Longitudinal studies allow social scientists to distinguish short from long-term phenomena, such as poverty. If the poverty rate is 10% at a point in time, this may mean that 10% of the population are always poor or that the whole population experiences poverty for 10% of the time.
When longitudinal studies are observational, in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect causal relationships than experiments. However, because of the repeated observation at the individual level, they have more power than cross-sectional observational studies, by virtue of being able to exclude time-invariant unobserved individual differences and also of observing the temporal order of events. Some of the disadvantages of longitudinal study are that they are time-consuming and expensive. Therefore, they are not convenient.Longitudinal studies can be retrospective (looking back in time, thus using existing data such as medical records or claims database) or prospective (requiring the collection of new data).Cohort studies are one type of longitudinal study which sample a cohort (a group of people who share a defining characteristic, typically who experienced a common event in a selected period, such as birth or graduation) and perform cross-section observations at intervals through time. However, not all longitudinal studies are cohort studies, as longitudinal studies can instead include a group of people who do not share a common event.Longitudinal studies do not require large numbers of participants (as in the examples below). Qualitative longitudinal studies may include only a handful of participants, and longitudinal pilot or feasibility studies often have fewer than 100 participants.
how is aspect ratio of a wing related to longitudinal static stability (LSS)?
like, if we increase the aspect ratio, is it going to increase or decrease the longitudinal static stability (LSS)?
suppose we have an aircraft whose centre of gravity is fixed at a particular location, if the...
Can anyone provide an elementary argument for why the zero mass of the photon means that it can't be longitudinally polarized?
I know of at least one non-elementary argument, which is that if you write down the Proca equation, it only has longitudinally polarized solutions if the mass is...
At the simulators:
http://wildcat.phys.northwestern.edu/vpl/waves/wavetypes.html
http://www.ngsir.netfirms.com/englishhtm/Lwave.htm
The velocity of each particle between two successive collisions is obviously not constant and it is defined by harmonic oscillation equations.
What a...
Homework Statement
Can somebody please explain me:
What does it mean that Longitudinal Stiffness (EA) is equal to infinity? What does it change if for some members of a structure "EA = infinity", and for other members "EA = finite number". Homework Equations
I know that we use longitudinal...
Homework Statement
In the situations where a transverse or longitudinal wave is propagating through a medium, the medium moves. How do you determine the speed of the medium's motion? When is the medium's speed at a maximum?
Homework Equations
The speed of the propagating wave is v = frequency...
Hi people,
I have a question which i hope you helpful guys/gals can help to shed light on.
We all know when we strike one end of a solid metal rod with a hammer sideways (i.e. from left to right), longitudinal vibrations will be set up across the length of the rod. Textbooks and websites...
We have 2 kind of mechanical wave, which is transversal and longitudinal. In calculating the kinetic energy we just integrate dm v^2 of course. Also in calculating the potential energy of an element of a longitudinal wave we can do it by making it as a small spring with a constant k' and just...
Homework Statement
The speed of sound in a metal rod is 3600 m s -1. The rod is 1.20m
long and clamped at one of its ends.
(a) Determine the frequency of its vibration if longitudinal waves
are established in the rod and it is vibrating in its first overtone
mode.
(d) Determine the...
Homework Statement
What property of the photon is responsible for the absence of longitudinal polarization?
Homework Equations
The Attempt at a Solution
I thought it is because of the presence of its angular momentum. Is it true?
Can anyone explain how to relate the bunch length and energy spread of a bunch in an electron storage ring to the longitudinal emittance? Also, if you know of a good reference I could use to look up more information I would really appreciate it. Thanks!
\DeltaHomework Statement
Consider a string with mass density \mu0 stretched between x=0 and x=a. Let the equilibrium tension be T0. Longitudinal waves are possible if the tension of the string varies as it stretches or compresses. For a piece of this string with equilibrium length L, a small...
Homework Statement
a longitudinal wave in a 6.0m long spring has a frequency of 10.0 Hz and a wavelength of 0.75m. calculate the speed of the wave and the time that it would take to travel the length of the spring.
Homework Equations
v = f (wavelength)
The Attempt at a Solution
v =...
hey friends please solve my problem
Both longitudinal and transverse waves can propagate through a solid. A wave on the surface of a liquid can involve both longitudinal and transverse motion of elements of the medium. On the other hand, a wave propagating through the volume of a fluid must be...
Homework Statement
A vet is using an ultrasonic motion detector to detect the heartbeat of an unborn chimp baby and claims that the speed of sound in the soft tissue of a chimp should be 1489 m/s. According to the manual which comes with the motion detector, the emitted frequency of sound...
Homework Statement
Please explain the difference and try to give examples. I know that the displacement of the medium in a transverse wave is perpendicular to the direction of wave travel and in longitudinal is parallel to the direction of wave travel, but does this mean that transverse waves...
I want to be able to differentiate between longitudinal(P) and Shear(S) waves in solids. Using one Acoustic emission (AE) senor placed 2 to 20 cm form a AE source e.g. a stress induced crack or pencil lead test, how can one detect both the P and S waves and determine what part of the receive...
Why is it that when a longitudinal wave is represented by a (pressure/position) and a (displacement/position) graph does the displacement 0 represent a compression or rarefaction
(maximum or minimum pressure)?
Homework Statement
Show that all longitudinal waves must be electrostatic by using Faraday's law.
Homework Equations
Faraday's law:
\frac{\partial \vec{B}}{\partial t} = - \nabla \times \vec{E}
The Attempt at a Solution
Where should I start??
This one has me pretty well stumped, I've tried several methods and I am basically getting tunnel vision now. Any help would be appreciated.
Homework Statement
(a) Show that the speed of a longitudinal wave along a spring of force constant 'k' is v=\sqrt{kL/\mu}, where L is the unstretched...
seeking help..please
why do low frequency contributes a low pitch?how?& why only longitudinal in fluids?can any1 please explain to me,tq please..:smile:
Hi everybody,
In chapter 10 of Kittel's "Introduction to Solid State Physics" it is said that the zeros of the dielectric functions determine the frequency of the longitudinal modes of oscillation, \epsilon(\omega_L) = 0, Eq. (17).
Am I missing something or this is actually an "unproved claim"...
I know that when a Longitudinal (Sound) Wave spreads in water the displacement
of the water particles is parallel to the direction of wave propagation and the displacement
equation looks like this :
y(x,t)=A*sin[2*π*f*(t-x/u)]
where : A=Amplitude, π=3.14..., f=frequency, u=speed of...
I know that when a Longitudinal (Sound) Wave spreads in water the displacement
of the water particles is parallel to the direction of wave propagation and the displacement
equation looks like this :
y(x,t)=A*sin[2*π*f*(t-x/u)]
where : A=Amplitude, π=3.14..., f=frequency, u=speed...
Hi guys, this is Barton Zwiebach's Introduction to String theory question 4.2 on the longitudinal wave on a taut string. The problem is purely classical and I seem to obtain a solution which seems far too complicated for me. If anyone has the answers it would be great, if not just your help...
Hi guys, this is Barton Zwiebach's Introduction to String theory question 4.2 on the longitudinal wave on a taut string. The problem is purely classical and I seem to obtain a solution which seems far too complicated for me. If anyone has the answers it would be great, if not just your help...
Why can’t longitudinal waves be polarized? I’m guessing its something to do with the particles oscillating in the same direction of propagation, but I can’t think of a explanation of why they can’t be polarized.
I have also been told that some transverse waves can’t be polarized. X-rays can...
Pretty basic question, i think, it's either possible or it's not.
Physics practical using an ultrasound generator and receiver components (in separate circuits, with the the generator rigged up to signal generator, and the receiver connected to an oscilloscope to take readings from). For the...
So we are working on sound waves in my physics course now and I was doing some textbook reading. I have been following it pretty well, but I just came across a relationship that I am not quite following.
It is with reference to wave interference. Let us say that two sound waves are emitted...
"Calculate the initial diameter of a wire that has been longitudinally strained by 30% and whose final diameter is 0.1cm. Assume no volume change."
Now I know that if there is no volume change, v=poisson's ratio= 0.5. Thus the lateral strain would equal 30%*0.5= 15%. But when I plug it...
Homework Statement
A small object of length dL is placed on the axis of a converging mirror of focal length f. The center of the object is a distance o from the mirror. Determine the length of the image and thus effective determine a longitudinal m' = dL'/dL for the lens.
Homework...
Hi. I am hoping someone can be of assistance in helping me solve a problem.
I am trying to calculate the longitudinal elongation of the steel bar shown in the attachment. I don't know where to start, so if anyone could point me in the right direction such as which formula I should use I would...
Sound is just Longitudinal vibrations of air that are detected from objects like the ear. Hence it originates from a vibrator.
For humans this vibrator is in the neck in the form of a vocal cord. So sound from humans really comes from the neck and the vibrations of air ascend up the neck and...
transverse longitudinal waves : slinky lab!
so this lab we did is called the transmission and reflection of a one-dimensional transverse wave...
1. we created a transverse pulse from one side and observed a point near the middle of the spring as the pulse passed...
- > so i wrote that it just...
Sir,
It is said that it is possible to distinguish between transverse and longitudinal waves by studying the property of polarization. Also it is said that longitudinal waves cannot be polarized but transverse waves can be polarized. Are they true?
Am I right to assume that a tall, thin, and rigid rod will likely fail under transverse loading (that is, perpendicular to its length) ? Similarly, would a tall, thin, and rigid rod do well under longitudinal stress?
hello
im just confusing about the electrical conduction in the electrical circuits
I mean, for example,
-an alternate voltage means that the electrons move back and forth in the circuit?
-if really this happens, then the electric waves in the circuit are LONGITUDINAL, because by definition...
Hello!
Okay, here we go.
Q1. A block is resting on top of a flat plate that is oscillating vertically with simple harmonic motion. If the frequency of the plate's oscillation is 2.0 Hz, what is the maximum amplitude it can have before the block loses contact with the plate?
- This...
i've found 2 equations on longitudinal velocity of waves v=lambda*freq and v=Lsqrt(k/m). is the 2nd equation derived from the 1st? if not how do you derive it? thx.
I'm confused by something my book says. For reference, here is the relevant text:
Figure 18-5b shows an oscillating element of air of cross-sectional area A and thickness \Delta x, with its center displaced from its equilibrium position by a distance s.
From Eq. 18-2 we can write, for the...
I don't recall what thread it was in but there was a comment that F = ma for a relativistic mass. I stated it was incorrect but did not provide a proof since it was a bit involved and too mathy for latex so instead of doing the latex out I made a new web page. For the derivation of the correct...