Погрешность измерения оказалась низкой.

Because измерения depends on погрешность and means of measurement / measurement-related.

In Russian, one noun often modifies another by going into the genitive:

• погрешность измерения = the error of measurement / measurement error
• результат эксперимента = the result of the experiment
• начало урока = the beginning of the lesson

So here:

• погрешность = the error / margin of error
• измерения = of measurement

This is singular genitive of измерение.

Both can be translated as error, but they are not used in exactly the same way.

• ошибка usually means a mistake, something wrong someone did
• погрешность is more technical: measurement error, inaccuracy, deviation, or margin of error

So in a scientific or technical sentence, погрешность is the natural word.
If you said ошибка измерения, it could also exist, but it sounds less precise and may suggest a mistake in the measuring process rather than the numerical inaccuracy itself.

Оказалась means something like turned out to be or proved to be.

So:

• Погрешность измерения была низкой = the measurement error was low
• Погрешность измерения оказалась низкой = the measurement error turned out to be low

The version with оказалась adds the idea that this became clear after checking, calculating, or examining the results.

That nuance is very common in Russian:

• Результат оказался лучше, чем ожидали. = The result turned out better than expected.
• Эксперимент оказался успешным. = The experiment turned out to be successful.

Because after оказаться, Russian normally uses the instrumental case for the predicate adjective or noun.

So:

• погрешность = feminine singular nominative
• низкой = feminine singular instrumental of низкая

This pattern is very common after verbs such as:

• быть in some contexts
• оказаться = to turn out to be
• стать = to become
• являться = to be / to constitute

Examples:

• Он оказался правым. = He turned out to be right.
• Она стала известной. = She became famous.
• Метод оказался эффективным. = The method turned out to be effective.

So низкой agrees with погрешность, but it appears in the instrumental, not the nominative.

It is the past tense, feminine singular, reflexive form of оказаться.

Breakdown:

• оказа- = verb stem
• -л- = past tense marker
• -а = feminine singular ending
• -сь = reflexive particle

It agrees with the subject погрешность, which is a feminine noun.

Compare:

• результат оказался = masculine
• погрешность оказалась = feminine
• условие оказалось = neuter
• данные оказались = plural

Yes, оказаться is a reflexive verb in form, but here it is best learned as a whole dictionary word with the meaning to turn out to be.

In many Russian verbs, -ся / -сь does not have a straightforward English reflexive meaning like oneself. Sometimes it does, but often it is just part of the verb’s normal form.

So it is better to memorize:

• оказать = to render / to provide / to show
• оказаться = to turn out to be / to find oneself

In this sentence, оказаться is simply the standard verb choice for turned out to be.

Yes, but it is a different structure and style.

• Погрешность измерения оказалась низкой = the measurement error turned out to be low
• Погрешность измерения низка = the measurement error is low

The second sentence uses the short-form adjective низка, which is more concise and often sounds more formal, written, or scientific.

So both are possible, but they are not identical:

• оказалась низкой emphasizes the result of evaluation
• низка simply states the property

Russian often uses низкий with things like levels, rates, values, and indicators, even where English might prefer low or sometimes small.

So низкая погрешность is perfectly natural Russian.

Other common combinations:

• низкая температура = low temperature
• низкая скорость = low speed
• низкий уровень шума = low noise level
• низкая вероятность = low probability

You may also hear небольшая погрешность = a small error / a slight inaccuracy, but низкая sounds especially natural in technical contexts when talking about a measured level or degree.

Not in this sentence. Here измерения is singular genitive of измерение.

That is one of those forms that can look confusing, because измерения can also be:

• nominative plural: measurements
• accusative plural
• singular genitive: of measurement

Here it is singular genitive because it depends on погрешность:

• погрешность чего? — измерения

If you wanted error of measurements in the plural, you would usually say:

• погрешность измерений

That would mean the error associated with multiple measurements.

The given word order is neutral and natural:

• Погрешность измерения оказалась низкой.

Russian word order is flexible, but changes in order usually affect emphasis.

For example:

• Погрешность измерения оказалась низкой.
  Neutral: the measurement error turned out to be low.

• Низкой оказалась погрешность измерения.
  More emphasis on низкой.

• Оказалась низкой погрешность измерения.
  More literary or report-like, with focus on the finding.

For learners, the original order is the safest and most standard choice.

The stress is:

• погрЕшность
• измерЕния
• оказАлась
• нИзкой

So the whole sentence is pronounced:

погрЕшность измерЕния оказАлась нИзкой

Stress is important in Russian, because it is not reliably predictable and can change from form to form.

Yes, it sounds fairly technical, scientific, or report-like because of words like погрешность and the overall structure.

A native speaker would expect this kind of sentence in contexts such as:

• lab reports
• engineering discussions
• statistics
• physics or mathematics
• technical documentation

In everyday conversation, people would more often use simpler words unless they are specifically talking about measurements or calculations.