frequency

Examples of frequency in the following topics:

• Cumulative Frequency Distributions

  • A cumulative frequency distribution displays a running total of all the preceding frequencies in a frequency distribution.
  • A cumulative frequency distribution is the sum of the class and all classes below it in a frequency distribution.
  • Rather than displaying the frequencies from each class, a cumulative frequency distribution displays a running total of all the preceding frequencies.
  • Constructing a cumulative frequency distribution is not that much different than constructing a regular frequency distribution.
  • The second column should be labeled Frequency.

• Relative Frequency Distributions

  • To find the relative frequencies, divide each frequency by the total number of data points in the sample.
  • Relative frequency distributions is often displayed in histograms and in frequency polygons.
  • The only difference between a relative frequency distribution graph and a frequency distribution graph is that the vertical axis uses proportional or relative frequency rather than simple frequency.
  • Just like we use cumulative frequency distributions when discussing simple frequency distributions, we often use cumulative frequency distributions when dealing with relative frequency as well.
  • To find the cumulative relative frequencies, add all the previous relative frequencies to the relative frequency for the current row.

• Frequency of Sound Waves

  • The perception of frequency is called pitch.
  • The perception of frequency is called pitch.
  • The SI unit of frequency is called a Hertz, denoted Hz.
  • Different species can hear different frequency ranges.
  • Three flashing lights, from lowest frequency (top) to highest frequency (bottom). f is the frequency in hertz (Hz); or the number of cycles per second.

• Do It Yourself: Plotting Qualitative Frequency Distributions

  • Sometimes a relative frequency distribution is desired.
  • Bar graphs for relative frequency distributions are very similar to bar graphs for regular frequency distributions, except this time, the y-axis will be labeled with the relative frequency rather than just simply the frequency.
  • This pie chart shows the frequency distribution of a bag of Skittles.
  • This graph shows the relative frequency distribution of a bag of Skittles.
  • This graph shows the frequency distribution of a bag of Skittles.

• Guidelines for Plotting Frequency Distributions

  • In statistics, the frequency (or absolute frequency) of an event is the number of times the event occurred in an experiment or study.
  • These frequencies are often graphically represented in histograms.
  • The relative frequency (or empirical probability) of an event refers to the absolute frequency normalized by the total number of events.
  • The height of a rectangle is also equal to the frequency density of the interval, i.e., the frequency divided by the width of the interval.
  • A histogram may also be normalized displaying relative frequencies.

• Radio Waves

  • The lowest commonly encountered radio frequencies are produced by high-voltage AC power transmission lines at frequencies of 50 or 60 Hz.
  • In this case, a carrier wave having the basic frequency of the radio station (perhaps 105.1 MHz) is modulated in frequency by the audio signal, producing a wave of constant amplitude but varying frequency.
  • Other channels called UHF (ultra high frequency) utilize an even higher frequency range of 470 to 1000 MHz.
  • Frequency modulation for FM radio.
  • (a) A carrier wave at the station's basic frequency.

• Period and Frequency

  • The period is the duration of one cycle in a repeating event, while the frequency is the number of cycles per unit time.
  • The frequency is defined as the number of cycles per unit time.
  • Frequency is usually denoted by a Latin letter f or by a Greek letter ν (nu).
  • Note that period and frequency are reciprocals of each other .
  • Sinusoidal waves of various frequencies; the bottom waves have higher frequencies than those above.

• Beats

  • The wave resulting from the superposition of two similar-frequency waves has a frequency that is the average of the two.
  • This wave fluctuates in amplitude, or beats, with a frequency called the beat frequency.
  • We can determine the beat frequency mathematically by adding two waves together.
  • One can also measure the beat frequency directly.
  • The number of beats per second, or the beat frequency, shows the difference in frequency between the two notes.

• RLC Series Circuit: At Large and Small Frequencies; Phasor Diagram

  • Response of an RLC circuit depends on the driving frequency—at large enough frequencies, inductive (capacitive) term dominates.
  • Now, we will examine the system's response at limits of large and small frequencies.
  • At large enough frequencies $(\nu \gg \frac{1}{\sqrt{2\pi LC}})$, XL is much greater than XC.
  • The impedance Z at small frequencies $(\nu \ll \frac{1}{\sqrt{2\pi LC}})$ is dominated by the capacitive term, assuming that the frequency is high enough so that XC is much larger than R.
  • Distinguish behavior of RLC series circuits as large and small frequencies

• Wavelength, Frequency, and Pitch

  • The word that musicians use for frequency is pitch.
  • The shorter the wavelength, the higher the frequency, and the higher the pitch, of the sound.
  • Instead of measuring frequencies, musicians name the pitches that they use most often.
  • (See Octaves and Diatonic Music and Tuning Systems for more on naming specific frequencies. ) These notes have frequencies (Have you heard of the "A 440" that is used as a tuning note?
  • So why should we bother talking about frequency, when musicians usually don't?