When your Performance score fluctuates it's usually because of changes in underlying conditions. Common problems include:. Lighthouse's documentation on Variability covers this in more depth. Furthermore, even though Lighthouse can provide you a single overall Performance score, it might be more useful to think of your site performance as a distribution of scores, rather than a single number.
See the introduction of User-Centric Performance Metrics to understand why. The Performance score is a weighted average of the metric scores. Naturally, more heavily weighted metrics have a bigger effect on your overall Performance score.
The metric scores are not visible in the report, but are calculated under the hood. The weightings are chosen to provide a balanced representation of the user's perception of performance. The weightings have changed over time because the Lighthouse team is regularly doing research and gathering feedback to understand what has the biggest impact on user-perceived performance.
Total raw scores combination of continuous assessment and end-of-semester examination are converted according to the following scheme:.
All continuous assessment results shall be displayed on the departmental notice boards two 2 weeks before the start of end-of-semester examinations.
The classifications are as follows:. Transcript shall reflect all courses taken or attempted by the student including audited courses , and the grades earned. TIMSS tests students in grades 4 and 8 in mathematics and science every 4 years.
The results show that. Average scores are one measure of achievement in national and international studies. However, they provide a very narrow perspective on student performance. Score gaps between high performers and low performers can be one indication of equity within an education system.
Here, high performers are those who scored in the 90th percentile or top 10 percent within their education system, and low performers are those who scored in the 10th percentile or bottom 10 percent within their education system. In , while some education systems had a higher average TIMSS score than the United States, none of these education systems had a wider score gap between their high and low performers than the United States.
The numbers on the horizontal axis are test scores, from The bars for each individual score tell you how many students received that score frequencies are on the vertical axis. The bars for the scores around 10 the average are the highest, and they get shorter the further you move to the left of the right, since fewer and fewer students receive scores that are far away from the average.
Now look at the second graph, which is, let's say, the same test and number of students but a very different distribution. In the second graph, the scores are clustered fairly compactly, whereas in the first graph there is much more variation among scores. They are one way to measure this spread around the average. They are typically expressed in the same metric as the measure in this case, test score points , and they are always a positive number.
In general, the more variation there is from the average, or the less clustered are observations around the mean, the higher the standard deviation. And this can matter. If, for example, these are two groups of students taking the same test, the two graphs present rather different pictures of how each set of students is performing. A teacher looking at the first graph might have to pay a bit more attention to differentiated instruction, as she is dealing with a wider spread of measured performance.
But what do the actual numbers mean? For instance, if we say that a given score is one standard deviation above the mean, what does that tell us? Perhaps the easiest way to begin thinking about this is in terms of percentiles. Roughly speaking, in a normal distribution , a score that is 1 s. On the flip side, a score that is one s. Moving further out into the tails of the curve, a score 2 s. In other words, roughly 95 percent of students are within two standard deviations — positive or negative — of the average.
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