The quantile or probit function, as you can see from the link (see "Computatuon"), is computed with inverse gaussian error function which I hope is downloadable for calculators like TI-89. Look here for instance.

Answer from ttnphns on Stack Exchange
🌐
Statology
statology.org › home › how to find quartiles using mean & standard deviation
How to Find Quartiles Using Mean & Standard Deviation
September 27, 2021 - You can use the following formulas to find the first (Q1) and third (Q3) quartiles of a normally distributed dataset: Q1 = μ - (.675)σ Q3 = μ + (.675)σ
🌐
University of North Dakota
cs.uni.edu › › ~campbell › stat › normfact.html
Important z-scores
It is readily calculated that for the standard normal distribution the first quartile is -.67 (using .2514 for .25) and the third quartile is .67.
🌐
YouTube
youtube.com › watch
Find the Quartiles of any Normal Distribution in 2 Minutes - YouTube
Introducing the four quartiles of the normal distribution and how to find them fast.👉Click here for all videos related to normal distribution: https://www.y...
Published   March 24, 2023
🌐
Stack Exchange
math.stackexchange.com › questions › 3531672 › finding-quartile-of-normal-distribution
quantile - Finding quartile of normal distribution - Mathematics Stack Exchange
... $\begingroup$ The quartile is not where x= 1/4 but where $N(x;\mu, k^2)= 1/4$. You need to use a table of the normal distribution to find x such that $\Phi\left(\frac{x-2}{9}\right)= 0.25$. And then, of course, "= 0.50" and "= 0.75".
🌐
Quora
quora.com › How-do-you-find-the-first-quartile-of-a-normal-distribution
How to find the first quartile of a normal distribution - Quora
Answer (1 of 2): You will need either a calculator which can calculate a normal distribution or a table of the normal distribution. I am using the table at Standard Normal Distribution Table Then you have to do a backward lookup of 0.25. In other words, find numbers as close as you can to 0.25 i...
🌐
YouTube
youtube.com › watch
Find the first Quartile Q_1 with the Normal Distribution and StatCrunch - YouTube
Please Subscribe here, thank you!!! https://goo.gl/JQ8NysFind the first Quartile Q_1 with the Normal Distribution and StatCrunch
Published   September 4, 2018
🌐
MathBitsNotebook
mathbitsnotebook.com › Algebra2 › Statistics › STstandardNormalDistribution.html
Standard Normal Distribution - MathBitsNotebook(A2)
Algebra 2 Lessons and Practice is a free site for students (and teachers) studying a second year of high school algebra.
Find elsewhere
Top answer
1 of 3
4

The answer is No, not exactly anyhow.

If you have two quartiles of a normal population then you can find $\mu$ and $\sigma.$ For example the lower and upper quantiles of $\mathsf{Norm}(\mu = 100,\, \sigma = 10)$ are $93.255$ and $106.745,$ respectively.

qnorm(c(.25, .75), 100, 10)
 [1]  93.2551 106.7449

Then $P\left(\frac{X-\mu}{\sigma} < -0.6745\right) = 0.25$ and $P\left(\frac{X-\mu}{\sigma} < 0.6745\right) = 0.75$ provide two equations that can be solved to find $\mu$ and $\sigma.$

qnorm(c(.25,.75))
[1] -0.6744898  0.6744898

However, sample quartiles are not population quartiles. There is not enough information in any normal sample precisely to determine $\mu$ and $\sigma.$

And you are not really sure your sample is from a normal population. If the population has mean $\mu$ and median $\eta,$ then the sample mean and median, respectively, are estimates of these two parameters. If the population is symmetrical, then $\mu = \eta,$ but you say the sample mean and median do not agree. So you cannot be sure the population is symmetrical, much less normal.

2 of 3
4

Based on @whuber's Comments about 'modeling', I gave some thought to relatively elementary methods that might be used to estimate the parameters of a normal distribution given the sample size, sample quartiles, and sample mean, assuming that data are normal.

Most of this will work better for very large $n.$ After some experimentation, I found that sample sizes around 35 are just large enough to get reasonably good results. All computations are done using R; seeds (based on current dates) are shown for simulations.

Hypothetical sample: So let's suppose we have a sample (rounded to two places) that is known to have come from a normal population of size $n = 35,$ but with unknown $\mu$ and $\sigma.$ We are given that the sample mean is $A = 49.19,$ the sample median is $H = 47.72,$ and that the lower and upper quartiles are $Q_1 = 43.62,\, Q_3 = 54.73,$ respectively. (Sometimes reports and articles don't give complete datasets, but do give such summary data about the sample.)

Estimating the population mean. The best estimate of the population mean $\mu$ is the sample mean $A = \hat \mu = 49.19.$

Estimating the population standard deviation: If we knew it, a good estimate of the population standard deviation (SD) would be the sample SD $S,$ but that information is not given. The interquartile range (IQR) of a standard normal population $1.35,$ and the IQR of a very large normal sample would be about $1.35\sigma.$

diff(qnorm(c(.25, .75)))
[1] 1.34898
set.seed(1018); IQR(rnorm(10^6))
[1] 1.351207

The IQR of our sample of size $n = 35$ is $54.73 - 43.62 = 11.11$ and the expected IQR of a standard normal sample of size 35 is 1.274. So we can estimate $\sigma$ for our population using the sample IQR: $\check \sigma = 11.11/1.274 = 8.72.$

set.seed(910);  m = 10^6;  n = 25
iqr = replicate(m, IQR(rnorm(n)))
mean(iqr);  sd(iqr)
[1] 1.274278
[1] 0.3024651

Assessing results: Thus, we can surmise that our normal population distribution is roughly, $\mathsf{Norm}(49.19, 8.72).$ Actually, I simulated the sample from $\mathsf{Norm}(50, 10).$

set.seed(2018);  x = round(rnorm(35, 50, 10), 2);  summary(x)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  31.73   43.62   47.72   49.19   54.73   70.99

It seems worthwhile to make two comparisons: (a) how well does the given information match the CDF of $\mathsf{Norm}(49.19, 8.72),$ and (b) how well does the CDF of this estimated distribution match what we know to be the true normal distribution. Of course, in a practical situation, we would not know the true normal distribution, so the second comparison would be impossible.

In the figure below, the blue curve is the estimated CDF; the solid red points show the sample values $Q_1, H, Q_3,$ and the red circle shows $A.$ The CDF of the true normal distribution is shown as a broken curve. It is no surprise that the three values $Q_1, Q_3,$ and $A$ used to estimate normal parameters fall near the estimated normal CDF.

curve(pnorm(x, 49.19, 8.27), 0, 80, lwd=2, ylab="CDF", 
    main="CDF of NORM(49.19, 8.27)", xaxs="i", col="blue")
  abline(h=0:1, col="green2")
  points(c(43.62, 47.72, 54.73), c(.25, .5, .75), pch=19, col="red")
  curve(pnorm(x, 50, 10), add=TRUE, lty="dotted")
  points(49.19, .50, col="red")

About symmetry: A remaining question is how much concern might have been appropriate about the normality of the data, upon noting that the sample mean exceeds the sample median by $D = A - H = 49.19 - 47.72 = 1.47.$ We can get a good idea by simulating the difference $D = A - H$ for many samples of size $n = 35$ from $\mathsf{Norm}(\mu = 49.19, \sigma = 8.27).$ A simple simulation shows that a larger positive difference might occur in such a normal sample about 11% of the time.

set.seed(918);  m = 10^6;  n = 25;  d = numeric(m)
for (i in 1:m) { 
   y = rnorm(n, 49.19, 8.27)
   d[i] = mean(y) - median(y) }
mean(d > 1.47)
[1] 0.113

Thus there is no significant evidence of skewness in the comparison of the our sample mean and median. Of course, the Laplace and Cauchy families of distributions are also symmetrical, so this would hardly be "proof" that the sample is from a normal population.

🌐
Allthingsstatistics
allthingsstatistics.com › home › quartiles for normal distribution
Quartiles for Normal Distribution - All Things Statistics
April 8, 2023 - Let X be a random variable that follows the normal distribution with mean μ and variance σ2. The quartiles of the normal distribution refer to those values of the random variable which divide the area under the probability distribution curve into exactly four equal parts.
🌐
Tidsskrift for Den norske legeforening
tidsskriftet.no › en › 2020 › 06 › medisin-og-tall › mean-and-standard-deviation-or-median-and-quartiles
Mean and standard deviation or median and quartiles? | Tidsskrift for Den norske legeforening
June 11, 2020 - The quartiles are defined as the 25th percentile and the 75th percentile. Hence, for the normal distribution, these define a narrower interval than does one standard deviation on each side of the mean.
🌐
SlideShare
slideshare.net › home › education › quartiles by using normal distribution
Quartiles by using normal distribution | PPT
December 31, 2020 - It shows that for a normal distribution, Q1 is equal to the mean minus 0.67 standard deviations, or 89.95. Q3 is equal to the mean plus 0.67 standard deviations, or 110.05. The document demonstrates how to use the normal distribution and z-table ...
🌐
Varsity Tutors
varsitytutors.com › ap_statistics-help › how-to-find-the-quartiles-for-a-set-of-data
How to find the quartiles for a set of data - AP Statistics
Using a normal table or calculator (such as R, using the command qnorm(0.9)), we get that the approximate -percentile is about . ... In order to find the first and third quartiles, we haave to find the 25th and 75th percentiles, respectively.
🌐
Scribbr
scribbr.com › home › quartiles & quantiles | calculation, definition & interpretation
Quartiles & Quantiles | Calculation, Definition & Interpretation
June 21, 2023 - To find the quartiles of a probability distribution, you can use the distribution’s quantile function.
🌐
Wikipedia
en.wikipedia.org › wiki › Quartile
Quartile - Wikipedia
October 30, 2025 - Therefore, it would be more likely to find data that are marked as outliers. The Excel function QUARTILE.INC(array, quart) provides the desired quartile value for a given array of data, using Method 3 from above.
🌐
Quora
quora.com › How-do-you-find-quartiles-with-mean-and-standard-deviation
How to find quartiles with mean and standard deviation - Quora
Answer (1 of 2): If you know the probability distribution (e.g., is it an exponential distribution - Gaussian, chi-square), then you can easily compute it using the probability density function. If you do not know the distribution, this is not enough information. You might estimate it by presumi...